Holiday Calendar

com.modernmustardseed/holiday-calendar · v1.0.1 · productivity

Holiday Calendar is healthy: it completed an MCP handshake in 505 ms and exposes 5 tools.

U.S. federal holidays with observed dates and business-day math. Example from an open-source kit.

Endpoint: https://starter.modernmustardseed.com/holidays (streamable-http)

Facts

Checked (UTC)	Status	Latency	Error
2026-10-15T22:35:11.667Z	Healthy	505
2026-10-14T20:40:39.266Z	Healthy	1425

`list_federal_holidays`	List the eleven U.S. federal holidays for one calendar year (2021 through 2100): each holiday's name, its actual date and weekday, the date it is observed when it falls on a weekend (Saturday moves to the Friday before, Sunday to the Monday after), and the rule that sets it, from 5 U.S.C. 6103. Use
`next_federal_holidays`	Find the next one to eleven U.S. federal holidays observed on or after a date, with each one's observed date and how many calendar days away it is. Without from_date it starts from today's date in America/New_York and says which date it used.
`check_business_day`	Check whether a date is a U.S. business day (a weekday that is not an observed federal holiday). Returns the weekday, the holiday observed that day if any, and the business days just before and just after it.
`add_business_days`	Move a number of U.S. business days forward or backward from a date, skipping weekends and observed federal holidays, for due dates, delivery windows and notice periods. The start date is not counted: 1 business day after a Friday is the next Monday, or Tuesday when that Monday is a holiday. Returns
`count_business_days`	Count the U.S. business days between two dates, both dates included, leaving out weekends and observed federal holidays. Returns the business day count, the weekend days, and each holiday that fell in the span. Spans up to 3,660 calendar days.