# Count US Federal Working Days

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

- Calculator id: `us-federal-working-days-between` · Category: Everyday Life (`everyday`) · Tool name: `count_us_federal_working_days`
- Canonical page: https://tttkmbb.com/everyday/us-federal-working-days-between · This document: https://tttkmbb.com/everyday/us-federal-working-days-between.md · JSON definition: https://tttkmbb.com/everyday/us-federal-working-days-between.json

## Purpose

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

**Use when:** 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.


## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `start_date` | date |  | required | First date in 2026-2027. |
| `end_date` | date |  | required | Last date in 2026-2027. |
| `include_start_date` | boolean |  | optional, default true | Whether start_date participates. |
| `include_end_date` | boolean |  | optional, default true | Whether end_date participates. |

## Output

| Field | Type | Unit | 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. |

## 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.

## Data Sources

- U.S. Office of Personnel Management Federal Holidays — https://www.opm.gov/policy-data-oversight/pay-leave/federal-holidays/ (government, published 2026-09-29)
- OPM Federal Holidays - In Lieu Of Determination — https://www.opm.gov/policy-data-oversight/pay-leave/work-schedules/fact-sheets/federal-holidays-in-lieu-of-determination/ (government_guidance)
- 5 U.S.C. 6103 — https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title5-section6103&num=0&edition=prelim (legislation)

Data freshness: `static`. Pinned OPM 2026-2027 package.

## API

- `GET https://tttkmbb.com/api/v1/calculate/us-federal-working-days-between?start_date=…&end_date=…`
- `POST https://tttkmbb.com/api/v1/calculate/us-federal-working-days-between` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/us-federal-working-days-between · OpenAPI operationId `count_us_federal_working_days` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool: `count_us_federal_working_days` (dedicated) or `run_calculator` with `{"calculator_id": "us-federal-working-days-between", "inputs": {…}}`

## Example

- US federal July 2027: inputs `{"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
```

## Limitations

You need a state/local/private-employer/exchange or alternate work-schedule calendar. Normalize endpoints, apply endpoint flags, and count the OPM calendar over the CLDR US weekend baseline. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Is this a general US business calendar?**

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

## Related

- [US Federal Holiday Working Day](https://tttkmbb.com/everyday/us-federal-working-day.md) — Inspect a date and its source basis.