Julian / Gregorian dates
Convert the same civil day between explicitly selected Julian and Gregorian calendars.
Your inputs
Choose your dates and the calculation convention. Results update as you edit.
Calculations run in your browser. Inputs are not saved or sent to analytics.
Your result
Complete the inputs to see your result.
How it works
- Source calendar → Julian day number → Resulting date
Assumptions and limitations
Both calendars are extended mathematically over years 1–9999. The selected calendar is explicit; no country’s historical adoption date is inferred.
Sources
- US Naval Observatory — Calendars and conversion algorithms Sources reviewed: 2026-10-05
- US Naval Observatory — Calendar leap rules and historical adoption Sources reviewed: 2026-10-05
