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Olly

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Add 5 business days" is harder than it looks. Here's an API for it

#api #javascript #python #productivity

"Delivered in 5 working days" sounds simple until Christmas falls on a Friday, Boxing Day is observed on the Monday, and your customer is in Scotland. CalKit gives you public holidays for 250+ countries and their regions, business-day maths that skips them, and timezone lookups.

curl -G "https://calkit-public-holidays-business-days-timezones.p.rapidapi.com/business-days/add" \
  -d date=2026-12-23 -d days=5 -d country=GB -d subdiv=ENG \
  -H "X-RapidAPI-Key: YOUR_RAPIDAPI_KEY" \
  -H "X-RapidAPI-Host: calkit-public-holidays-business-days-timezones.p.rapidapi.com"
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The response gives the result date and lists every holiday it skipped: Christmas Day, Boxing Day, Boxing Day (observed) and New Year's Day.

Endpoints

  • /holidays?country=GB&year=2026&subdiv=ENG: every public holiday in the year.
  • /is-holiday?date=2026-12-25&country=GB: whether that date is a holiday, a weekend or a business day.
  • /next-holiday?country=US&count=3: the next holidays and how many days away each one is.
  • /business-days/between: SLA and invoice-terms maths, including custom weekends such as fri,sat.
  • /timezone?lat=51.45&lng=-2.59: the IANA zone, offset and DST status for any coordinate.
  • /convert?time=2026-10-14T09:30&from=Europe/London&to=America/New_York: convert a time between zones.

MCP

For agents, the MCP server is at https://calkit-public-holidays-business-days-timezones.p.rapidapi.com/mcp.

There's a free plan. CalKit on RapidAPI

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