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Count US Federal Working Days

Counts US federal-baseline working and non-working dates using the OPM 2026-2027 schedule.

When to use

You need an auditable federal-employee/office working-day count for a pinned year.

Do not use when: You need a state/local/private-employer/exchange or alternate work-schedule calendar.

Example user requests

Count US federal working days from 2027-07-01 to 2027-07-10.

Formula

for each included date: working_days += US federal status.is_working_day

Normalize endpoints, apply endpoint flags, and count the OPM calendar over the CLDR US weekend baseline.

Inputs

Parameter	Type	Required	Description
`start_date`	date	yes	First date in 2026-2027.
`end_date`	date	yes	Last date in 2026-2027.
`include_start_date`	boolean	default true	Whether start_date participates.
`include_end_date`	boolean	default true	Whether end_date participates.

Outputs

Output	Type	Description
`normalized_start_date`	date	Earlier endpoint.
`normalized_end_date`	date	Later endpoint.
`working_days`	integer	US federal-baseline working dates.
`non_working_days`	integer	Weekend and OPM federal-holiday dates.
`federal_holidays_counted`	list	OPM events in the range.
`territory`	string	US.
`territory_name`	string	United States.
`day_type`	string	Regular weekday, regular weekend or OPM federal holiday.
`holiday_names`	string_list	OPM federal holiday names applying on the date.
`holiday_observed`	boolean	True when the date is the OPM in-lieu/observed date for a holiday whose actual date is a weekend.
`holiday_actual_dates`	string_list	Underlying statutory holiday dates for observed events.
`weekend_days`	string_list	CLDR Saturday/Sunday baseline.
`rest_day_policy`	string	OPM alternative work schedules need separate in-lieu resolution.
`calendar_scope`	string	Federal employees and federal offices only.
`calendar_profile`	string	us-opm-federal-holidays.
`source_quality`	string	Official OPM schedule and federal-law references.
`dataset_version`	string	Pinned OPM evidence package.
`sources`	list	Official OPM, federal guidance and legislation sources.

Example

US federal July 2027: {"start_date":"2027-07-01","end_date":"2027-07-10","include_start_date":true,"include_end_date":true} → {"working_days":6}

GET https://tttkmbb.com/api/v1/calculate/us-federal-working-days-between?start_date=2027-07-01&end_date=2027-07-10&include_start_date=true&include_end_date=true

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/us-federal-working-days-between (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/us-federal-working-days-between · Markdown: https://tttkmbb.com/everyday/us-federal-working-days-between.md · JSON definition: https://tttkmbb.com/everyday/us-federal-working-days-between.json
MCP: server https://tttkmbb.com/mcp, tool count_us_federal_working_days
OpenAPI operationId: count_us_federal_working_days
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

U.S. Office of Personnel Management Federal Holidays (government)
OPM Federal Holidays - In Lieu Of Determination (government_guidance)
5 U.S.C. 6103 (legislation)

FAQ

Is this a general US business calendar?

No. It is explicitly scoped to the OPM federal schedule.

Related calculators

US Federal Holiday Working Day — Inspect a date and its source basis.