tilwhen date engine

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Deterministic date arithmetic with auditable receipts: business days, due dates, holidays.

Utilities

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add_days Read-only

The date N whole calendar days after a date (exclusive counting: the start date is day 0). Omit date for today in tz. For working days use business_days; for the gap between two dates use days_between.

daysinteger, required

Whole calendar days to add. Negative counts backwards.

tzstring

IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.

datestring

ISO date YYYY-MM-DD, or "today" (resolved in tz)

Tools (9)

add_days

read-only

Argument	Type	Description
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
date	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
days*	integer	Whole calendar days to add. Negative counts backwards.

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "days"
  ],
  "properties": {
    "tz": {
      "type": "string",
      "default": "UTC",
      "maxLength": 64,
      "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC."
    },
    "date": {
      "type": "string",
      "default": "today",
      "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$",
      "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)"
    },
    "days": {
      "type": "integer",
      "maximum": 100000,
      "minimum": -100000,
      "description": "Whole calendar days to add. Negative counts backwards."
    }
  },
  "additionalProperties": false
}

business_days

Span mode (from+to): business days between two dates, exclusive of the start day, inclusive of the end day. Add mode (days, optional date): the date N business days away. Passing from or to selects span mode and needs both; days and date are then ignored, so add mode takes its start date in date, not from. Optional holiday jurisdiction or custom calendar, and a selectable working week. For calendar days use add_days, subtract_days or days_between.

read-only

Argument	Type	Description
to	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
date	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
days	integer	Add mode: business days to move. Negative counts backwards.
from	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
workweek	string	Working week. Default mon-fri (Sat+Sun weekend).
jurisdiction	string	Holiday jurisdiction id: US, GB, GB-SCT, GB-NIR, IE, FR, CA, AU, UG (alias UK for GB). No default: omit for no holiday calendar.

days_between

Signed whole calendar days from the from date to the to date, midnight to midnight in tz: positive when to is later, negative when it is earlier. Endpoints are exclusive, so this is the gap and consecutive dates are 1 apart. Either date may be "today", resolved in tz. For working days between two dates use business_days; to move a date by N days use add_days or subtract_days.

read-only

Argument	Type	Description
to*	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
from*	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "from",
    "to"
  ],
  "properties": {
    "to": {
      "type": "string",
      "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$",
      "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)"
    },
    "tz": {
      "type": "string",
      "default": "UTC",
      "maxLength": 64,
      "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC."
    },
    "from": {
      "type": "string",
      "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$",
      "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)"
    }
  },
  "additionalProperties": false
}

explain

Runs any operation and returns the receipt plus human-readable derivation steps. Set op, then pass the fields that operation's own tool takes. Use it when the user asks how an answer was reached.

read-only

Argument	Type	Description
op*	string	Operation to explain. holiday_lookup is the holidays tool; the others share their tool's name.
to	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
net	integer	Net-N payment terms in calendar days (Net 30 = 30).
date	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
days	integer	Day count for add_days, subtract_days and business_days add mode.
from	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
roll	boolean	Roll a weekend or holiday due date forward to the next business day. Default false.
year

holidays

Observed public holidays with the nominal (legal) date and status: rule (statutory) or declared (officially declared for that year). Declared-only holidays are omitted for undeclared years, with a holiday_data_incomplete warning.

read-only

Argument	Type	Description
year*	integer	Calendar year to list, e.g. 2027
jurisdiction*	string	Holiday jurisdiction id: US, GB, GB-SCT, GB-NIR, IE, FR, CA, AU, UG (alias UK for GB).

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "jurisdiction",
    "year"
  ],
  "properties": {
    "year": {
      "type": "integer",
      "maximum": 3000,
      "minimum": 1600,
      "description": "Calendar year to list, e.g. 2027"
    },
    "jurisdiction": {
      "type": "string",
      "maxLength": 8,
      "description": "Holiday jurisdiction id: US, GB, GB-SCT, GB-NIR, IE, FR, CA, AU, UG (alias UK for GB)."
    }
  },
  "additionalProperties": false
}

invoice_due

Due date for Net-N payment terms (calendar days, invoice date = day 0). Optional roll-forward past weekends and, with a jurisdiction or custom calendar, public holidays.

read-only

Argument	Type	Description
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
net*	integer	Net-N payment terms in calendar days (Net 30 = 30).
roll	boolean	Roll a weekend or holiday due date forward to the next business day. Default false.
workweek	string	Working week. Default mon-fri (Sat+Sun weekend).
invoiceDate	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
jurisdiction	string	Holiday jurisdiction id: US, GB, GB-SCT, GB-NIR, IE, FR, CA, AU, UG (alias UK for GB). No default: omit for no holiday calendar.
customHolidays	array	Custom organizational holiday calendar as ISO dates (mutually exclusive with jurisdiction)

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "net"
  ],
  "properties": {
    "tz": {
      "type": "string",
      "default": "UTC",
      "maxLength": 64,
      "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC."
    },
    "net": {
      "type": "integer",
      "maximum": 3650,
      "minimum": 0,
      "description": "Net-N payment terms in calendar days (Net 30 = 30)."
    },
    "roll": {
      "type": "boolean",
      "description": "Roll a weekend or holiday due date forward to the next business day. Default false."
    },
    "workweek": {
      "enum": [
        "mon-fri",
        "sun-thu",
        "mon-sat"
      ],
      "type": "string",
      "description": "Working week. Default mon-fri (Sat+Sun weekend)."
    },
    "invoiceDate": {
      "type": "string",
      "default": "today",
      "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$",
      "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)"
    },
    "jurisdiction": {
      "type": "string",
      "maxLength": 8,
      "description": "Holiday jurisdiction id: US, GB, GB-SCT, GB-NIR, IE, FR, CA, AU, UG (alias UK for GB). No default: omit for no holiday calendar."
    },
    "customHolidays": {
      "type": "array",
      "items": {
        "type": "string"
      },
      "maxItems": 1000,
      "description": "Custom organizational holiday calendar as ISO dates (mutually exclusive with jurisdiction)"
    }
  },
  "additionalProperties": false
}

next_occurrence

The next occurrence strictly after the base date (default today) of either a tracked event slug (e.g. "christmas") or a weekday (0 = Sunday .. 6 = Saturday). Provide exactly one of event/weekday.

read-only

Argument	Type	Description
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
from	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
event	string	Event slug (e.g. christmas). Exactly one of event/weekday.
weekday	integer	0 = Sunday .. 6 = Saturday. Exactly one of event/weekday.

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "properties": {
    "tz": {
      "type": "string",
      "default": "UTC",
      "maxLength": 64,
      "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC."
    },
    "from": {
      "type": "string",
      "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$",
      "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)"
    },
    "event": {
      "type": "string",
      "maxLength": 40,
      "description": "Event slug (e.g. christmas). Exactly one of event/weekday."
    },
    "weekday": {
      "type": "integer",
      "maximum": 6,
      "minimum": 0,
      "description": "0 = Sunday .. 6 = Saturday. Exactly one of event/weekday."
    }
  },
  "additionalProperties": false
}

parse_date_query

Parses queries like "90 business days from today in uganda" into a normalized operation, answers it, and returns the auditable receipt. Ambiguous dates (03/04/2027) return needsClarification instead of a guess.

read-only

Argument	Type	Description
q*	string	The date question in plain language. Pass the user's wording rather than a date you computed.
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
locale	string	Resolves ambiguous slash dates; omit to receive clarification choices

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "q"
  ],
  "properties": {
    "q": {
      "type": "string",
      "maxLength": 200,
      "minLength": 1,
      "description": "The date question in plain language. Pass the user's wording rather than a date you computed."
    },
    "tz": {
      "type": "string",
      "default": "UTC",
      "maxLength": 64,
      "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC."
    },
    "locale": {
      "enum": [
        "mdy",
        "dmy"
      ],
      "type": "string",
      "description": "Resolves ambiguous slash dates; omit to receive clarification choices"
    }
  },
  "additionalProperties": false
}

subtract_days

The date N whole calendar days before a date (exclusive counting: the start date is day 0). Omit date for today in tz. For working days use business_days; for the gap between two dates use days_between.

read-only

Argument	Type	Description
tz	string	IANA timezone that defines "today" (e.g. Africa/Kampala). Default UTC.
date	string	ISO date YYYY-MM-DD, or "today" (resolved in tz)
days*	integer	Whole calendar days to subtract. Negative counts forwards.

Input schema (JSON)

{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "days"
  ],
  "properties": {
    "tz": {
      "type": "string",
      "default": "UTC",
      "maxLength": 64,
      "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC."
    },
    "date": {
      "type": "string",
      "default": "today",
      "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$",
      "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)"
    },
    "days": {
      "type": "integer",
      "maximum": 100000,
      "minimum": -100000,
      "description": "Whole calendar days to subtract. Negative counts forwards."
    }
  },
  "additionalProperties": false
}

{ "type": "object", "$schema": "http://json-schema.org/draft-07/schema#", "required": [ "op" ], "properties": { "op": { "enum": [ "add_days", "subtract_days", "days_between", "business_days", "invoice_due", "next_occurrence", "holiday_lookup" ], "type": "string", "description": "Operation to explain. holiday_lookup is the holidays tool; the others share their tool's name." }, "to": { "type": "string", "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$", "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)" }, "tz": { "type": "string", "default": "UTC", "maxLength": 64, "description": "IANA timezone that defines \"today\" (e.g. Africa/Kampala). Default UTC." }, "net": { "type": "integer", "maximum": 3650, "minimum": 0, "description": "Net-N payment terms in calendar days (Net 30 = 30)." }, "date": { "type": "string", "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$", "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)" }, "days": { "type": "integer", "maximum": 100000, "minimum": -100000, "description": "Day count for add_days, subtract_days and business_days add mode." }, "from": { "type": "string", "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$", "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)" }, "roll": { "type": "boolean", "description": "Roll a weekend or holiday due date forward to the next business day. Default false." }, "year": { "type": "integer", "maximum": 3000, "minimum": 1600, "description": "Calendar year for holiday_lookup, e.g. 2027" }, "event": { "type": "string", "maxLength": 40, "description": "Event slug (e.g. christmas). Exactly one of event/weekday." }, "weekday": { "type": "integer", "maximum": 6, "minimum": 0, "description": "0 = Sunday .. 6 = Saturday. Exactly one of event/weekday." }, "workweek": { "enum": [ "mon-fri", "sun-thu", "mon-sat" ], "type": "string", "description": "Working week. Default mon-fri (Sat+Sun weekend)." }, "invoiceDate": { "type": "string", "pattern": "^(\\d{4}-\\d{2}-\\d{2}|today)$", "description": "ISO date YYYY-MM-DD, or \"today\" (resolved in tz)" }, "jurisdiction": { "type": "string", "maxLength": 8, "description": "Holiday jurisdiction id: US, GB, GB-SCT, GB-NIR, IE, FR, CA, AU, UG (alias UK for GB). No default: omit for no holiday calendar." }, "customHolidays": { "type": "array", "items": { "type": "string" }, "maxItems": 1000, "description": "Custom organizational holiday calendar as ISO dates (mutually exclusive with jurisdiction)" } }, "additionalProperties": false }