Julian date

Today, Thursday, 12 November 2026, is 26316 in the YYDDD format (year 26, day 316) and 2026316 in YYYYDDD. The astronomical Julian Day Number is 2461357, and the Modified Julian Day is 61356.

It is the last two digits of the year followed by the day of the year from 001 to 365 (366): 26316 means day 316 of 2026. The format is used on food and medicine packaging, in the military and on mainframes. Strictly it is an ordinal date (ISO 8601: YYYY-DDD), not a date in the Julian calendar.

The “Julian date” of industry (YYDDD) is simply the day of the year. The Julian Day (JD) of astronomers counts days continuously since noon on 1 January 4713 BC, with a fraction for the time. The Julian calendar is the calendar of Julius Caesar, today 13 days behind the Gregorian one.

MJD = JD − 2400000.5: it starts at midnight instead of noon and counts the days since 17 November 1858, which gives shorter numbers. It is used in astronomy, geodesy and satellite navigation.

Date to YYDDD (date in A1): =TEXT(A1,"yy")&TEXT(A1-DATE(YEAR(A1),1,0),"000"). YYDDD to date (text in A1): =DATE(2000+LEFT(A1,2),1,RIGHT(A1,3)) for years from 2000. Date to Julian Day: =A1+2415018.5 for a date at 00:00.