March 14, 2025

Julian Dates

2 minutes

Happy Friday! It’s the 73rd day of the year. And to astronomers and a few others, it’s day 2,460,749. That’s the tally under the Julian Date system. Its starting point was more than 6700 years ago.

The system was created by Joseph Scaliger, a French scholar and religious leader, in 1583. The system was named for his father, Julius.

Scaliger was trying to integrate the many calendars that had been used throughout history. He picked a starting point long before any known calendar system. In the modern calendar, it was November 24th, 4714 B.C. That’s a date when long cycles of the Sun, Moon, and an ancient Roman cycle for collecting taxes all intersected.

Astronomers use the Julian Date system to record observations and events. And they don’t add minutes or seconds – they convert those to decimals. That makes it easier to compare the timing of their work to observations made long ago, or under different calendar systems or time zones. They don’t have to figure out the permutations of the calendars or other details – just subtract one date from another to find the difference.

A Julian day begins at noon Universal Time – 7 a.m. Central Daylight Time. So day 2,460,749 begins at 7 a.m. today, and ends 24 hours later – on the Ides of March.

Script by Damond Benningfield

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By Billy Henry

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