About OpenDay API
OpenDay API is a JB Studio service that answers one question precisely: which days are holidays, and which are business days, in the US and Puerto Rico?
Last verified: October 16, 2026Sources & methodologyFound an error? Tell us
What it is
A REST API covering 53 regions: US federal, all 50 states and DC, Federal Reserve bank days, and the legal, government and banking calendars of Puerto Rico. It also does business-day math and has Puerto Rico data (municipios, ZIP codes and IVU). It is sold on Apify and billed per successful request.
Who it is for
- Payroll and HR software: paydays and leave that fall on holidays.
- Banks, credit unions and fintech: Federal Reserve settlement days.
- Shipping and delivery: “arrives in N business days”.
- Legal and compliance: “within N business days” deadlines.
- Spanish-language apps: every holiday has a Spanish name.
How the data is verified
Every date cites the law or official calendar it comes from, with a link, and carries a label: official, computed or projected. Each year we compare the dates with the published official calendars, and every version of this site passes an automatic check of all its dates. Sources & methodology.
Who publishes it
OpenDay API is published by JB Studio. For questions, corrections or support: jbstudiotemplate@gmail.com.