What is today's Julian date?

It depends on which one you need. The ordinal date of October 26, 2026 is 26299 (YYDDD) or 2026299 (YYYYDDD); the astronomical Julian Date at noon UT that day is 2461340.0. The converter opens on today's date for both.

What is a Julian Date in astronomy?

A continuous count of days since noon Universal Time on January 1, 4713 BC, with the time of day as a decimal fraction. Astronomers and variable-star observers use it because it needs no months, years or time zones: the time between two observations is a plain subtraction.

What is the Modified Julian Date?

The Julian Date minus 2,400,000.5. It gives smaller numbers and starts at midnight instead of noon: MJD 0 is midnight UT at the start of November 17, 1858, and January 1, 2000 at 12:00 UT is MJD 51544.5.

How do I read a 5-digit Julian date like 26299?

The first two digits are the year and the last three the day of the year: 26299 is day 299 of 2026, which is October 26, 2026. A 7-digit code such as 2026299 writes the year in full. Switch the ordinal tab to "Ordinal (Julian) date → date" and type the code.

Why do food and military labels use Julian dates?

Because a day-of-the-year code is short, sorts in order and reads the same in every country. Canned goods, US egg cartons and military supplies often print pack or production dates this way. It is properly called an ordinal date; ISO 8601 writes it as 2026-299.

How do I convert a Julian date in Excel?

For a date in A1: =TEXT(A1,"yy")&TEXT(A1-DATE(YEAR(A1),1,0),"000") gives YYDDD, and =A1+2415018.5 gives the astronomical Julian Date at midnight (for dates from March 1, 1900). Back from a 5-digit code in A1: =DATE(2000+LEFT(A1,2),1,RIGHT(A1,3)).

What is the difference between the Julian and Gregorian calendars?

The leap-year rule. The Julian calendar has a leap year every 4 years; the Gregorian calendar, introduced in 1582, skips three of them every 400 years. The two have drifted apart by 13 days since March 1, 1900, so a Julian date plus 13 days is the Gregorian date until February 2100.

Is a Julian Date the same as a Julian calendar date?

No. A Julian Date is a day count used in astronomy, such as 2461340.0 for noon UT on October 26, 2026; a Julian calendar date is a day, month and year in the calendar Julius Caesar introduced, which some Orthodox churches still use for their holidays. October 26, 2026 is October 13, 2026 in the Julian calendar.

Julian Date Converter

"Julian date" means three different things, and this converter does all three. Astronomers' Julian Date (JD), as AAVSO observers report it, and the Modified Julian Date; the ordinal "Julian" date of food, military and manufacturing labels, as YYDDD or YYYYDDD; and dates in the old Julian calendar, converted to and from the Gregorian calendar. Each tab converts both ways.

Convert

DateTime (UT)

Pick a date and a time.

How to use the Julian date converter

1
Pick the kind of Julian date
Julian Day for astronomy, ordinal date for label codes, or Julian calendar for old dates.
2
Choose the direction
Convert to the Julian form, or back from it.
3
Enter the date or the number
The conversion appears as you type; copy the link to share it.

How DateMath converts Julian dates

DateMath counts the Julian Date as the days and fractions of a day since noon Universal Time on January 1, 4713 BC (proleptic Julian calendar), so a date at midnight UT ends in .5, and the Modified Julian Date subtracts 2400000.5. The ordinal date is the year and the day of the year, 26299 for October 26, 2026. Julian and Gregorian calendar dates are converted through their Julian Day Number, which is the same for the same day in both calendars.

Julian Day and the Julian calendar. DateMath counts the astronomers' Julian Date as the days since noon Universal Time on January 1, 4713 BC in the proleptic Julian calendar, so January 1, 2000 at 12:00 UT is JD 2451545.0, and the Modified Julian Date is JD − 2400000.5, which starts at midnight. Julian calendar dates have a leap year every 4 years, with no century rule. Source: Julian day, Julian calendar.
The Gregorian calendar. DateMath treats every date as a Gregorian date, with its leap-year rule: a year divisible by 4 is a leap year, except century years not divisible by 400, so 2000 had a February 29 and 2100 will not. Source: Gregorian calendar.

DateMath's date math is tested against more than 100 cases worked out by hand. Every worked example and table on the site is computed with the same code the calculators run, so a page and its calculator can't disagree.

Three things called a Julian date

Searchers, labels and software use “Julian date” for three different numbers, so check which one you have before you convert it:

The Julian Date (JD) of astronomy: a count of days, with decimals for the time, since noon UT on January 1, 4713 BC. Saturday, January 1, 2000 at noon UT is JD 2451545.00000. Variable-star observers, such as those reporting to the AAVSO, time their observations this way.
The ordinal date, often called a Julian date on food packs, in the military and in manufacturing: the year and the day of the year, such as 27060 for March 1, 2027 (YYDDD) or 2027060 (YYYYDDD).
A date in the Julian calendar, the calendar before the Gregorian reform of 1582, still used by some Orthodox churches: January 7, 2027 in the Gregorian calendar is December 25, 2026 in the Julian calendar, which is why those churches celebrate Christmas on January 7.

Julian Date and Modified Julian Date (the AAVSO Julian date converter)

A Julian Date starts each day at noon UT, so a date at midnight ends in .5 and the integer part changes at noon. Enter times in Universal Time (UTC); for a time in a US zone, convert it first with the time zone converter. The Modified Julian Date is JD − 2,400,000.5, which starts the day at midnight and keeps the numbers shorter.

Moment	Date	JD	MJD
J2000.0, the astronomers' reference epoch	Saturday, January 1, 2000	2451545.00000	51544.50000
Start of the Unix timestamp count	Thursday, January 1, 1970	2440587.50000	40587.00000
MJD 0	Wednesday, November 17, 1858	2400000.50000	0.00000
Midnight UT, January 1, 2027	Friday, January 1, 2027	2461406.50000	61406.00000
Noon UT, July 1, 2027	Thursday, July 1, 2027	2461588.00000	61587.50000
6:00 PM UT, December 31, 2027	Friday, December 31, 2027	2461771.25000	61770.75000

To find the time between two observations, subtract their Julian Dates: the difference is in days, and times 24 in hours. That is the reason astronomers use one running count instead of calendar dates.

Julian date calendar 2027: the day of the year of each month

For a 5-digit code (YYDDD) the first two digits are the year and the last three the day of the year; a 7-digit code (YYYYDDD) writes the year in full. Add the day of the month minus 1 to the month's first day below: March 15, 2027 is 060 + 14 = 074, so 27074. In a leap year every day from March 1 is one higher.

Date	Day in 2027	Day in 2028 (leap year)	YYDDD in 2027
January 1	001	001	27001
February 1	032	032	27032
March 1	060	061	27060
April 1	091	092	27091
May 1	121	122	27121
June 1	152	153	27152
July 1	182	183	27182
August 1	213	214	27213
September 1	244	245	27244
October 1	274	275	27274
November 1	305	306	27305
December 1	335	336	27335

The converter reads a 5-digit code as a year from 2000 to 2099. Codes on older goods may mean the 1900s; the 7-digit form avoids the question.

Julian to Gregorian: how far apart the calendars are

The Julian calendar has a leap year every fourth year, century years included, so it gains a day on the Gregorian calendar in each century year that the Gregorian rule skips. At the reform, Thursday, October 4, 1582 (Julian) was followed by Friday, October 15, 1582 (Gregorian).

Gregorian dates	Julian date is behind by	Julian date of the first day
October 15, 1582 to February 28, 1700	10 days	October 5, 1582 (JDN 2299161)
March 1, 1700 to February 28, 1800	11 days	February 19, 1700 (JDN 2342032)
March 1, 1800 to February 28, 1900	12 days	February 18, 1800 (JDN 2378556)
March 1, 1900 to February 28, 2100	13 days	February 17, 1900 (JDN 2415080)
March 1, 2100 to February 28, 2200	14 days	February 16, 2100 (JDN 2488129)

The converter works through the Julian Day Number, which is the same for one day in both calendars, so it converts any date from the year 1 to 9999. Britain and its colonies changed calendars in September 1752, so British and American dates before then are usually Julian.

Julian dates in Excel

Date to YYDDD: =TEXT(A1,"yy")&TEXT(A1-DATE(YEAR(A1),1,0),"000"); to YYYYDDD: =YEAR(A1)*1000+A1-DATE(YEAR(A1),1,0).
YYDDD back to a date: =DATE(2000+LEFT(A1,2),1,RIGHT(A1,3)), formatted as a date.
Date and time to the astronomical Julian Date: =A1+2415018.5, and back with =A1-2415018.5. Excel counts days from 1900 with a February 29, 1900 that never existed, so the formula holds from March 1, 1900.

Frequently asked questions

What is today's Julian date?: It depends on which one you need. The ordinal date of October 26, 2026 is 26299 (YYDDD) or 2026299 (YYYYDDD); the astronomical Julian Date at noon UT that day is 2461340.0. The converter opens on today's date for both.
What is a Julian Date in astronomy?: A continuous count of days since noon Universal Time on January 1, 4713 BC, with the time of day as a decimal fraction. Astronomers and variable-star observers use it because it needs no months, years or time zones: the time between two observations is a plain subtraction.
What is the Modified Julian Date?: The Julian Date minus 2,400,000.5. It gives smaller numbers and starts at midnight instead of noon: MJD 0 is midnight UT at the start of November 17, 1858, and January 1, 2000 at 12:00 UT is MJD 51544.5.
How do I read a 5-digit Julian date like 26299?: The first two digits are the year and the last three the day of the year: 26299 is day 299 of 2026, which is October 26, 2026. A 7-digit code such as 2026299 writes the year in full. Switch the ordinal tab to "Ordinal (Julian) date → date" and type the code.
Why do food and military labels use Julian dates?: Because a day-of-the-year code is short, sorts in order and reads the same in every country. Canned goods, US egg cartons and military supplies often print pack or production dates this way. It is properly called an ordinal date; ISO 8601 writes it as 2026-299.
How do I convert a Julian date in Excel?: For a date in A1: =TEXT(A1,"yy")&TEXT(A1-DATE(YEAR(A1),1,0),"000") gives YYDDD, and =A1+2415018.5 gives the astronomical Julian Date at midnight (for dates from March 1, 1900). Back from a 5-digit code in A1: =DATE(2000+LEFT(A1,2),1,RIGHT(A1,3)).
What is the difference between the Julian and Gregorian calendars?: The leap-year rule. The Julian calendar has a leap year every 4 years; the Gregorian calendar, introduced in 1582, skips three of them every 400 years. The two have drifted apart by 13 days since March 1, 1900, so a Julian date plus 13 days is the Gregorian date until February 2100.
Is a Julian Date the same as a Julian calendar date?: No. A Julian Date is a day count used in astronomy, such as 2461340.0 for noon UT on October 26, 2026; a Julian calendar date is a day, month and year in the calendar Julius Caesar introduced, which some Orthodox churches still use for their holidays. October 26, 2026 is October 13, 2026 in the Julian calendar.

Julian Date Converter

How to use the Julian date converter

Pick the kind of Julian date

Choose the direction

Enter the date or the number