Convert a calendar date to its Julian day number, or a Julian day number back to a calendar date.
The Julian Day Number is a continuous count of days since a fixed reference point in 4713 BCE, widely used in astronomy and some scientific fields because it avoids the complications of calendar months and leap years.
Julian Day = (Unix Timestamp ÷ 86,400) + 2,440,587.5
January 1, 2026 has a Julian Day Number of approximately 2,461,041.5.
In astronomy, a continuous day count since a fixed reference point, used to simplify date math across long time spans without calendar complications.
No — the Julian calendar was a historical calendar system; Julian date is a numbering system still used today, especially in astronomy.
It avoids complications from varying month lengths, leap years, and calendar reforms, simplifying time-elapsed calculations.