Liturgical Calendar Grounding Data

Overview

Pass an integer month to fetch Catholic celebrations for the current year. Each response includes the event rank, liturgical season, vestment color, and whether the date is a holy day of obligation. Paid plans can specify custom years and receive additional lectionary cycles, psalter weeks, and season boundary dates.

Live Test Liturgical Calendar Grounding Data Source →

The tool

Once your client is connected to the VerveContext server, this appears in its tool list as LiturgicalCalendarGroundingData. It is read-only and open-world — it fetches and never mutates anything on your side — so most clients call it without asking you to confirm.

Tool call

{
  "name": "LiturgicalCalendarGroundingData",
  "arguments": {}
}

Connecting

One server URL covers every source in the catalog, including this one. Authorization is OAuth: the client opens a browser once, and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervecontext": {
      "url": "https://api.vervecontext.com/v1/mcp"
    }
  }
}

Per-client setup — Claude, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made. Premium arguments are accepted on every plan but only take effect on plans that include them.

Argument	Type	Description
`month`Optional	integer	The month to get Liturgical Calendar data for (default: current month) range 1–12
`year`OptionalPremium	integer	The year to get Liturgical Calendar data for (default: current year) range 1900–2100

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client reads fields without parsing prose. status is "ok" and error is null on success; a null field means the value was not available for that input, not that the call failed.

Result

{
  "status": "ok",
  "error": null,
  "data": {
    "2026-01-01": [
      {
        "id": "mary_mother_of_god",
        "precedence": "GENERAL_SOLEMNITY_3",
        "rank": "SOLEMNITY",
        "isHolyDayOfObligation": true,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-02": [
      {
        "id": "basil_the_great_and_gregory_nazianzen_bishops",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "christmas_time_january_2",
          "date": "2026-01-02",
          "dateDef": {
            "dateFn": "weekdayBeforeEpiphany",
            "dateArgs": [
              2
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:christmas_time.before_epiphany",
            {
              "day": 2
            }
          ],
          "seasons": [
            "CHRISTMAS_TIME"
          ],
          "periods": [
            "DAYS_BEFORE_EPIPHANY",
            "CHRISTMAS_TO_PRESENTATION_OF_THE_LORD"
          ],
          "colors": [
            "WHITE"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 2,
            "dayOfSeason": 9,
            "dayOfWeek": 5,
            "nthDayOfWeekInMonth": 1,
            "startOfSeason": "2025-12-25",
            "endOfSeason": "2026-01-11",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "CHRISTMAS_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_1"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ],
    "2026-01-03": [
      {
        "id": "christmas_time_january_3",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      },
      {
        "id": "most_holy_name_of_jesus",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "christmas_time_january_3",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "WHITE"
          ]
        }
      }
    ],
    "2026-01-04": [
      {
        "id": "second_sunday_after_christmas",
        "precedence": "UNPRIVILEGED_SUNDAY_6",
        "rank": "SUNDAY",
        "isHolyDayOfObligation": true,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-05": [
      {
        "id": "christmas_time_january_5",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-06": [
      {
        "id": "epiphany_of_the_lord",
        "precedence": "PROPER_OF_TIME_SOLEMNITY_2",
        "rank": "SOLEMNITY",
        "isHolyDayOfObligation": true,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-07": [
      {
        "id": "wednesday_after_epiphany",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      },
      {
        "id": "raymond_of_penyafort_priest",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "wednesday_after_epiphany",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "WHITE"
          ]
        }
      }
    ],
    "2026-01-08": [
      {
        "id": "thursday_after_epiphany",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-09": [
      {
        "id": "friday_after_epiphany",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-10": [
      {
        "id": "saturday_after_epiphany",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-11": [
      {
        "id": "baptism_of_the_lord",
        "precedence": "PROPER_OF_TIME_SOLEMNITY_2",
        "rank": "SOLEMNITY",
        "isHolyDayOfObligation": true,
        "isOptional": false,
        "colors": [
          "WHITE"
        ]
      }
    ],
    "2026-01-12": [
      {
        "id": "ordinary_time_1_monday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-13": [
      {
        "id": "ordinary_time_1_tuesday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      },
      {
        "id": "hilary_of_poitiers_bishop",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_1_tuesday",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "GREEN"
          ]
        }
      }
    ],
    "2026-01-14": [
      {
        "id": "ordinary_time_1_wednesday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-15": [
      {
        "id": "ordinary_time_1_thursday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-16": [
      {
        "id": "ordinary_time_1_friday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-17": [
      {
        "id": "anthony_of_egypt_abbot",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_1_saturday",
          "date": "2026-01-17",
          "dateDef": {
            "dateFn": "dateOfOrdinaryTime",
            "dateArgs": [
              6,
              1
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:ordinary_time.weekday",
            {
              "week": 1,
              "dow": 6
            }
          ],
          "seasons": [
            "ORDINARY_TIME"
          ],
          "periods": [
            "EARLY_ORDINARY_TIME"
          ],
          "colors": [
            "GREEN"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 1,
            "dayOfSeason": 6,
            "dayOfWeek": 6,
            "nthDayOfWeekInMonth": 3,
            "startOfSeason": "2026-01-12",
            "endOfSeason": "2026-11-28",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "ORDINARY_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_1"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ],
    "2026-01-18": [
      {
        "id": "ordinary_time_2_sunday",
        "precedence": "UNPRIVILEGED_SUNDAY_6",
        "rank": "SUNDAY",
        "isHolyDayOfObligation": true,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-19": [
      {
        "id": "ordinary_time_2_monday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-20": [
      {
        "id": "ordinary_time_2_tuesday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      },
      {
        "id": "fabian_i_pope",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "RED"
        ],
        "weekday": {
          "id": "ordinary_time_2_tuesday",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "GREEN"
          ]
        }
      },
      {
        "id": "sebastian_of_milan_martyr",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "RED"
        ],
        "weekday": {
          "id": "ordinary_time_2_tuesday",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "GREEN"
          ]
        }
      }
    ],
    "2026-01-21": [
      {
        "id": "agnes_of_rome_virgin",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "RED"
        ],
        "weekday": {
          "id": "ordinary_time_2_wednesday",
          "date": "2026-01-21",
          "dateDef": {
            "dateFn": "dateOfOrdinaryTime",
            "dateArgs": [
              3,
              2
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:ordinary_time.weekday",
            {
              "week": 2,
              "dow": 3
            }
          ],
          "seasons": [
            "ORDINARY_TIME"
          ],
          "periods": [
            "EARLY_ORDINARY_TIME"
          ],
          "colors": [
            "GREEN"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 2,
            "dayOfSeason": 10,
            "dayOfWeek": 3,
            "nthDayOfWeekInMonth": 3,
            "startOfSeason": "2026-01-12",
            "endOfSeason": "2026-11-28",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "ORDINARY_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_2"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ],
    "2026-01-22": [
      {
        "id": "ordinary_time_2_thursday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      },
      {
        "id": "vincent_of_saragossa_deacon",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "RED"
        ],
        "weekday": {
          "id": "ordinary_time_2_thursday",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "GREEN"
          ]
        }
      }
    ],
    "2026-01-23": [
      {
        "id": "ordinary_time_2_friday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-24": [
      {
        "id": "francis_de_sales_bishop",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_2_saturday",
          "date": "2026-01-24",
          "dateDef": {
            "dateFn": "dateOfOrdinaryTime",
            "dateArgs": [
              6,
              2
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:ordinary_time.weekday",
            {
              "week": 2,
              "dow": 6
            }
          ],
          "seasons": [
            "ORDINARY_TIME"
          ],
          "periods": [
            "EARLY_ORDINARY_TIME"
          ],
          "colors": [
            "GREEN"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 2,
            "dayOfSeason": 13,
            "dayOfWeek": 6,
            "nthDayOfWeekInMonth": 4,
            "startOfSeason": "2026-01-12",
            "endOfSeason": "2026-11-28",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "ORDINARY_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_2"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ],
    "2026-01-25": [
      {
        "id": "sunday_of_the_word_of_god",
        "precedence": "UNPRIVILEGED_SUNDAY_6",
        "rank": "SUNDAY",
        "isHolyDayOfObligation": true,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-26": [
      {
        "id": "timothy_of_ephesus_and_titus_of_crete_bishops",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_3_monday",
          "date": "2026-01-26",
          "dateDef": {
            "dateFn": "dateOfOrdinaryTime",
            "dateArgs": [
              1,
              3
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:ordinary_time.weekday",
            {
              "week": 3,
              "dow": 1
            }
          ],
          "seasons": [
            "ORDINARY_TIME"
          ],
          "periods": [
            "EARLY_ORDINARY_TIME"
          ],
          "colors": [
            "GREEN"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 3,
            "dayOfSeason": 15,
            "dayOfWeek": 1,
            "nthDayOfWeekInMonth": 4,
            "startOfSeason": "2026-01-12",
            "endOfSeason": "2026-11-28",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "ORDINARY_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_3"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ],
    "2026-01-27": [
      {
        "id": "ordinary_time_3_tuesday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      },
      {
        "id": "angela_merici_virgin",
        "precedence": "OPTIONAL_MEMORIAL_12",
        "rank": "OPTIONAL_MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": true,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_3_tuesday",
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "colors": [
            "GREEN"
          ]
        }
      }
    ],
    "2026-01-28": [
      {
        "id": "thomas_aquinas_priest",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_3_wednesday",
          "date": "2026-01-28",
          "dateDef": {
            "dateFn": "dateOfOrdinaryTime",
            "dateArgs": [
              3,
              3
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:ordinary_time.weekday",
            {
              "week": 3,
              "dow": 3
            }
          ],
          "seasons": [
            "ORDINARY_TIME"
          ],
          "periods": [
            "EARLY_ORDINARY_TIME"
          ],
          "colors": [
            "GREEN"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 3,
            "dayOfSeason": 17,
            "dayOfWeek": 3,
            "nthDayOfWeekInMonth": 4,
            "startOfSeason": "2026-01-12",
            "endOfSeason": "2026-11-28",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "ORDINARY_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_3"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ],
    "2026-01-29": [
      {
        "id": "ordinary_time_3_thursday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-30": [
      {
        "id": "ordinary_time_3_friday",
        "precedence": "WEEKDAY_13",
        "rank": "WEEKDAY",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "GREEN"
        ]
      }
    ],
    "2026-01-31": [
      {
        "id": "john_bosco_priest",
        "precedence": "GENERAL_MEMORIAL_10",
        "rank": "MEMORIAL",
        "isHolyDayOfObligation": false,
        "isOptional": false,
        "colors": [
          "WHITE"
        ],
        "weekday": {
          "id": "ordinary_time_3_saturday",
          "date": "2026-01-31",
          "dateDef": {
            "dateFn": "dateOfOrdinaryTime",
            "dateArgs": [
              6,
              3
            ],
            "yearOffset": 0
          },
          "dateExceptions": [],
          "alternativeTransferDateDefs": [],
          "precedence": "WEEKDAY_13",
          "rank": "WEEKDAY",
          "allowSimilarRankItems": false,
          "isHolyDayOfObligation": false,
          "isOptional": false,
          "i18nDef": [
            "seasons:ordinary_time.weekday",
            {
              "week": 3,
              "dow": 6
            }
          ],
          "seasons": [
            "ORDINARY_TIME"
          ],
          "periods": [
            "EARLY_ORDINARY_TIME"
          ],
          "colors": [
            "GREEN"
          ],
          "commonsDef": [],
          "martyrology": [],
          "titles": [],
          "calendar": {
            "weekOfSeason": 3,
            "dayOfSeason": 20,
            "dayOfWeek": 6,
            "nthDayOfWeekInMonth": 5,
            "startOfSeason": "2026-01-12",
            "endOfSeason": "2026-11-28",
            "startOfLiturgicalYear": "2025-11-30",
            "endOfLiturgicalYear": "2026-11-28",
            "seasons": [
              "ORDINARY_TIME"
            ]
          },
          "cycles": {
            "properCycle": "PROPER_OF_TIME",
            "sundayCycle": "YEAR_A",
            "weekdayCycle": "YEAR_2",
            "psalterWeek": "WEEK_3"
          },
          "fromCalendarId": "ProperOfTime",
          "fromExtendedCalendars": []
        }
      }
    ]
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`2026-01-01`	array[1]
`2026-01-01.0.id`	string	`mary_mother_of_god`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-01.0.precedence`Premium	string	`GENERAL_SOLEMNITY_3`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-01.0.rank`	string	`SOLEMNITY`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-01.0.isHolyDayOfObligation`	boolean	`true`	Whether Catholics are obligated to attend Mass for this event
`2026-01-01.0.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-01.0.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)
`2026-01-02`	array[1]
`2026-01-02.0.id`	string	`basil_the_great_and_gregory_nazianzen_bishops`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-02.0.precedence`Premium	string	`GENERAL_MEMORIAL_10`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-02.0.rank`	string	`MEMORIAL`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-02.0.isHolyDayOfObligation`	boolean	`false`	Whether Catholics are obligated to attend Mass for this event
`2026-01-02.0.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-02.0.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)
`2026-01-02.0.weekday`	object	`{…}`	The plain weekday this date would otherwise observe; present when the listed event is a memorial or optional memorial that takes precedence over, or is offered as an alternative to, the ordinary weekday. When that same weekday is also listed as its own celebration on the date, this nested copy carries only the summary fields (id, precedence, rank, isHolyDayOfObligation, isOptional, colors) and the deeper weekday.* fields below are absent
`2026-01-02.0.weekday.id`	string	`christmas_time_january_2`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-02.0.weekday.date`	string	`2026-01-02`
`2026-01-02.0.weekday.dateDef`	object	`{…}`
`2026-01-02.0.weekday.dateDef.dateFn`	string	`weekdayBeforeEpiphany`
`2026-01-02.0.weekday.dateDef.dateArgs`	array	`[2]`
`2026-01-02.0.weekday.dateDef.yearOffset`	number	`0`
`2026-01-02.0.weekday.dateExceptions`	array	`[]`
`2026-01-02.0.weekday.alternativeTransferDateDefs`	array	`[]`
`2026-01-02.0.weekday.precedence`Premium	string	`WEEKDAY_13`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-02.0.weekday.rank`	string	`WEEKDAY`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-02.0.weekday.allowSimilarRankItems`	boolean	`false`
`2026-01-02.0.weekday.isHolyDayOfObligation`	boolean	`false`	Whether Catholics are obligated to attend Mass for this event
`2026-01-02.0.weekday.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-02.0.weekday.i18nDef`	array	`["seasons:christmas_time.before_epiphany",{"day":2}]`
`2026-01-02.0.weekday.seasons`	array	`["CHRISTMAS_TIME"]`
`2026-01-02.0.weekday.periods`	array	`["DAYS_BEFORE_EPIPHANY","CHRISTMAS_TO_PRESENTATION_OF_THE_LORD"]`
`2026-01-02.0.weekday.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)
`2026-01-02.0.weekday.commonsDef`	array	`[]`
`2026-01-02.0.weekday.martyrology`	array	`[]`
`2026-01-02.0.weekday.titles`	array	`[]`
`2026-01-02.0.weekday.calendar`	object	`{…}`
`2026-01-02.0.weekday.calendar.weekOfSeason`	number	`2`
`2026-01-02.0.weekday.calendar.dayOfSeason`	number	`9`
`2026-01-02.0.weekday.calendar.dayOfWeek`	number	`5`
`2026-01-02.0.weekday.calendar.nthDayOfWeekInMonth`	number	`1`
`2026-01-02.0.weekday.calendar.startOfSeason`	string	`2025-12-25`
`2026-01-02.0.weekday.calendar.endOfSeason`	string	`2026-01-11`
`2026-01-02.0.weekday.calendar.startOfLiturgicalYear`	string	`2025-11-30`
`2026-01-02.0.weekday.calendar.endOfLiturgicalYear`	string	`2026-11-28`
`2026-01-02.0.weekday.calendar.seasons`	array	`["CHRISTMAS_TIME"]`
`2026-01-02.0.weekday.cycles`	object	`{…}`
`2026-01-02.0.weekday.cycles.properCycle`	string	`PROPER_OF_TIME`
`2026-01-02.0.weekday.cycles.sundayCycle`	string	`YEAR_A`
`2026-01-02.0.weekday.cycles.weekdayCycle`	string	`YEAR_2`
`2026-01-02.0.weekday.cycles.psalterWeek`	string	`WEEK_1`
`2026-01-02.0.weekday.fromCalendarId`	string	`ProperOfTime`
`2026-01-02.0.weekday.fromExtendedCalendars`	array	`[]`
`2026-01-03`	array[2]
`2026-01-03.0.id`	string	`christmas_time_january_3`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-03.0.precedence`Premium	string	`WEEKDAY_13`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-03.0.rank`	string	`WEEKDAY`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-03.0.isHolyDayOfObligation`	boolean	`false`	Whether Catholics are obligated to attend Mass for this event
`2026-01-03.0.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-03.0.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)
`2026-01-04`	array[1]
`2026-01-04.0.id`	string	`second_sunday_after_christmas`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-04.0.precedence`Premium	string	`UNPRIVILEGED_SUNDAY_6`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-04.0.rank`	string	`SUNDAY`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-04.0.isHolyDayOfObligation`	boolean	`true`	Whether Catholics are obligated to attend Mass for this event
`2026-01-04.0.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-04.0.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)
`2026-01-05`	array[1]
`2026-01-05.0.id`	string	`christmas_time_january_5`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-05.0.precedence`Premium	string	`WEEKDAY_13`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-05.0.rank`	string	`WEEKDAY`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-05.0.isHolyDayOfObligation`	boolean	`false`	Whether Catholics are obligated to attend Mass for this event
`2026-01-05.0.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-05.0.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)
`2026-01-06`	array[1]
`2026-01-06.0.id`	string	`epiphany_of_the_lord`	Unique identifier naming the liturgical event; also labels the nested weekday object when one is present
`2026-01-06.0.precedence`Premium	string	`PROPER_OF_TIME_SOLEMNITY_2`	Liturgical rank precedence level that determines which of several events on the same date is actually observed
`2026-01-06.0.rank`	string	`SOLEMNITY`	Liturgical rank classification of the event (e.g., WEEKDAY, MEMORIAL, FEAST, SOLEMNITY, SUNDAY)
`2026-01-06.0.isHolyDayOfObligation`	boolean	`true`	Whether Catholics are obligated to attend Mass for this event
`2026-01-06.0.isOptional`	boolean	`false`	Whether observing this event is left to choice rather than required, as with an optional memorial
`2026-01-06.0.colors`	array	`["WHITE"]`	Liturgical vestment colors worn for the event (e.g., PURPLE, WHITE, RED, GREEN)

Why ground on it

A model can produce something that looks like this answer from its training data, and be confidently out of date or simply wrong. This source returns the current value in a shape you can check, which is the difference between an answer you can cite and one you have to hedge.

Point an evaluation at 2026-01-01.0.id: it is the field most worth pinning a claim to, and it is either present and current or absent — never plausibly invented.

Failure modes

Errors come back as tool errors carrying a sentence the model can act on, not a bare status code. Error handling covers the full list.

Status	What it means
`400` / `422`	The arguments did not validate. The message names the offending one.
`401`	The OAuth session is invalid or expired — reconnect the server.
`403`	Blocked by a key restriction or an IP allow-list. Never a bad identity.
`404`	This source is not part of VerveContext. Check the catalog.
`429`	Out of credits, or a brief rate limit. The message tells them apart.

A call costs 2 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

Church Bulletin Publishing: When preparing weekly parish bulletins, church administrators pull upcoming feast ranks and vestment colors to format worship aids accurately.
Daily Missal Apps: Mobile prayer apps display daily commemorations and required vestment colors to orient users within the current Catholic season.
Sacristy Vestment Planning: To prepare altar paraments and priest vestments ahead of time, sacristans check the required liturgical color for upcoming celebrations.
Catholic School Scheduling: School administrators schedule all-school masses by checking which upcoming dates qualify as holy days of obligation.

Other ways to use Liturgical Calendar Grounding Data

Set up Liturgical Calendar Grounding Data on VerveContext, or reach the same source a different way. Your VerveContext account and credits work on all of them — one key, one balance.

Call it as a REST APIOne HTTPS endpoint and an x-api-key header, with SDKs for Node, Python and .NET.APIVerve →Reference →

Give it to an AI agentConnect over MCP and your agent calls it as a native tool — Claude, Cursor, ChatGPT.VerveKit →Reference →

Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.VerveSheets →Reference →