# Add US Federal Working Days

> Adds or subtracts dates using the pinned OPM federal schedule and US weekend baseline.

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

## Purpose

Adds or subtracts dates using the pinned OPM federal schedule and US weekend baseline.

**Use when:** You need a deterministic US federal employee/office date offset in 2026-2027.

**Do not use when:** You need state/local/private-employer, exchange or alternate-work-schedule semantics.

## Example user requests

- Add five US federal working days after 2027-06-17.


## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `start_date` | date |  | required | Gregorian start date in 2026-2027. |
| `working_days` | integer |  | required | Signed offset; start date is excluded for non-zero offsets. (min -1000, max 1000) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `start_date` | date |  | Input date. |
| `result_date` | date |  | Date reached. |
| `working_days_added` | integer |  | Signed requested offset. |
| `calendar_days_elapsed` | integer |  | Signed Gregorian difference. |
| `federal_holidays_skipped` | list |  | OPM federal holidays crossed. |
| `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

`move one day at a time; decrement remaining only when US federal status.is_working_day=true`

Skip the US weekend baseline and pinned OPM federal observed dates.

## 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-add-working-days?start_date=…&working_days=…`
- `POST https://tttkmbb.com/api/v1/calculate/us-federal-add-working-days` 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-add-working-days · OpenAPI operationId `add_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: `add_us_federal_working_days` (dedicated) or `run_calculator` with `{"calculator_id": "us-federal-add-working-days", "inputs": {…}}`

## Example

- Offset across Juneteenth: inputs `{"start_date":"2027-06-17","working_days":1}` → `{"result_date":"2027-06-21"}`

```
GET https://tttkmbb.com/api/v1/calculate/us-federal-add-working-days?start_date=2027-06-17&working_days=1
```

## Limitations

You need state/local/private-employer, exchange or alternate-work-schedule semantics. Skip the US weekend baseline and pinned OPM federal observed dates. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Does this resolve alternate federal schedules?**

No. The default result uses the Monday-Friday baseline; OPM's alternate work-schedule rules require the employee's schedule.

## Related

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