Is a Julian calendar date the same as an ordinal stamp or Julian Day Number?

No. An ordinal stamp such as 26245 means Gregorian year 2026, day 245. A Julian Day Number such as 2451545 is the astronomical running day count. A Julian calendar date has a year, month and day in the older calendar. For example, Gregorian 2026-09-02 is Julian calendar 2026-08-20. The calendar mode converts that third meaning in either direction.

How do I read a code like 26245?

The first two digits are the year and the last three are the day of the year: 26245 is day 245 of 2026, or 2 September. Day 001 is 1 January. Type a bare day number such as 245 for the current year, or a seven-digit code such as 2026245 for the full year. A code with a four-digit year and a separator, such as 2026-245, is also accepted. Four- and six-digit codes are rejected because this ordinal mode cannot split them unambiguously.

What year does a two-digit year like 26 mean?

This converter reads 26 as 2026 and all two-digit years as 2000 to 2099. A code without a century cannot identify one on its own. For another century, type the full year as 1999365 or 1999-365. Gregorian dates from year 0001 to 9999 are accepted.

How do leap years change the ordinal date?

Every date from 1 March onwards is one day later in a leap year, because 29 February takes day 060. So 1 March is day 060 in a common year and 061 in a leap year, and 31 December is day 365 or 366. Leap years follow the Gregorian rule, every fourth year except century years unless divisible by 400: 2024 and 2000 are leap years, 2100 is not. The converter refuses day 366 in a common year and says how many days that year has. The reference table shows both columns side by side.

What is the Julian Day Number, and why does the Julian Date start at noon?

The Julian Day Number is a running count of days with no months or years in the way, so the gap between two dates is one subtraction. Day 0 was 1 January 4713 BC in the old Julian calendar, chosen by Joseph Scaliger in 1583, and the count has never been reset: 1 January 2000 was JDN 2451545 and 2 September 2026 is 2461286. The Julian Date adds a fraction of the day, and that fraction is counted from noon UTC, because astronomers wanted a whole night's observing to fall on one number. So midnight UTC opening 1 January 2000 is JD 2451544.5, and if you type a Julian Date with a fraction the converter rounds it to the day it falls in and says so.

What is the Modified Julian Date?

The Julian Date minus 2400000.5. The half day moves the start of the day to midnight, and the 2400000 drops two digits, so a date this century is a five-digit number: 1 January 2000 is MJD 51544 and 2 September 2026 is MJD 61285. MJD 0 is 17 November 1858. It is used in satellite tracking, space telemetry and time-signal work. Pick MJD next to the field in JDN mode to type one directly, or read it from the list for any date.

What is today's Julian date?

The page opens on today, read from your device's own calendar, so the two large numbers at the top are today's ordinal stamp and today's Julian Day Number. The Today button brings any other date back to it. The date is read from your calendar rather than the UTC instant, so it is the day on your wall rather than the day in Greenwich, which is already tomorrow for part of the world every evening.

How do I convert between the Julian and Gregorian calendars?

Select Julian calendar, then Gregorian to Julian or Julian to Gregorian. Gregorian dates use the date picker. Type an old Julian calendar date as YYYY-MM-DD, including a Julian leap day such as 1900-02-29. That date becomes Gregorian 1900-03-13. Julian years divisible by four are leap years; Gregorian century years also need to be divisible by 400. The offset therefore changes over the centuries rather than staying at 13 days.

Does this convert historical dates using a country's calendar changeover?

Both calendars are applied throughout the supported range. No country-specific adoption date is used. Julian 1582-10-05 converts to Gregorian 1582-10-15, but dates around a local calendar changeover require knowing which calendar the record used.

Can I use military or egg-packaging Julian codes here?

For a day-of-year code, choose Ordinal to date. A bare three-digit day uses the current year, and YYDDD includes a two-digit year. The conversion identifies a calendar day; it does not determine shelf life, an expiration date or whether an item is safe to use. Manufacturer-specific codes and JD Edwards CYYDDD fields are not decoded.

Can I convert a date from 2024, 2025 or 2026?

Use the Date field to choose the year you need. Gregorian 2024 is a leap year with 366 days; 2025 and 2026 have 365. Today always means the current date from your device, even when an older year appears in a question.

Can I use this in a phone or desktop browser?

The converter runs in your browser. Use the date picker, or type a code into its labelled field. No account or upload is needed.

Does it calculate the Julian Date for a specific time?

The output lists Julian Date at midnight UTC for the chosen date. A fractional JD or MJD can be entered in JDN to date mode to identify its calendar day, but the result does not preserve the time of day. Heliocentric and barycentric corrections are not calculated.

What formula converts a Gregorian date to a Julian Day Number?

Using year Y, month M and day D, first set A = floor((14 - M) / 12), y = Y + 4800 - A and m = M + 12A - 3. Then JDN = D + floor((153m + 2) / 5) + 365y + floor(y / 4) - floor(y / 100) + floor(y / 400) - 32045. The Julian Date at midnight UTC is JDN - 0.5. An ordinal day number instead counts from 1 January in the same Gregorian year.

What date is Julian day 212 in 2026?

For the day-of-year meaning, day 212 of 2026 is 31 July. Its five-digit stamp is 26212 and its seven-digit stamp is 2026212. This is different from astronomical Julian Day Number 212, which falls outside the supported calendar range.

Julian Date Converter

Convert a Gregorian date to its ordinal day-of-year stamp, astronomical Julian Day Number and old Julian calendar date. Read a stamp or day number back to a date, or switch to Julian calendar to convert between the two calendars. Today is ready when the page opens.

Julian dateLoading today's date.

Mode

Date

Choose the meaning of Julian date. Ordinal stamps count days within a Gregorian year. Astronomical day numbers count days continuously. The Julian calendar uses its own leap-year rule. Gregorian output years run from 0001 to 9999, or Julian Day Number 1721426 to 5373484. Calendar conversion extends both calendars throughout that range, without a country-specific switch.

Ordinal day numbers by month

First and last ordinal day numbers for each Gregorian month in a common year and a leap year. Dates from 1 March onward are one higher in a leap year.

Month	1st, common year	1st, leap year	Last day, common year	Last day, leap year
January	001	001	031	031
February	032	032	059	060
March	060	061	090	091
April	091	092	120	121
May	121	122	151	152
June	152	153	181	182
July	182	183	212	213
August	213	214	243	244
September	244	245	273	274
October	274	275	304	305
November	305	306	334	335
December	335	336	365	366

Common questions

Is a Julian calendar date the same as an ordinal stamp or Julian Day Number?: No. An ordinal stamp such as 26245 means Gregorian year 2026, day 245. A Julian Day Number such as 2451545 is the astronomical running day count. A Julian calendar date has a year, month and day in the older calendar. For example, Gregorian 2026-09-02 is Julian calendar 2026-08-20. The calendar mode converts that third meaning in either direction.
How do I read a code like 26245?: The first two digits are the year and the last three are the day of the year: 26245 is day 245 of 2026, or 2 September. Day 001 is 1 January. Type a bare day number such as 245 for the current year, or a seven-digit code such as 2026245 for the full year. A code with a four-digit year and a separator, such as 2026-245, is also accepted. Four- and six-digit codes are rejected because this ordinal mode cannot split them unambiguously.
What year does a two-digit year like 26 mean?: This converter reads 26 as 2026 and all two-digit years as 2000 to 2099. A code without a century cannot identify one on its own. For another century, type the full year as 1999365 or 1999-365. Gregorian dates from year 0001 to 9999 are accepted.
How do leap years change the ordinal date?: Every date from 1 March onwards is one day later in a leap year, because 29 February takes day 060. So 1 March is day 060 in a common year and 061 in a leap year, and 31 December is day 365 or 366. Leap years follow the Gregorian rule, every fourth year except century years unless divisible by 400: 2024 and 2000 are leap years, 2100 is not. The converter refuses day 366 in a common year and says how many days that year has. The reference table shows both columns side by side.
What is the Julian Day Number, and why does the Julian Date start at noon?: The Julian Day Number is a running count of days with no months or years in the way, so the gap between two dates is one subtraction. Day 0 was 1 January 4713 BC in the old Julian calendar, chosen by Joseph Scaliger in 1583, and the count has never been reset: 1 January 2000 was JDN 2451545 and 2 September 2026 is 2461286. The Julian Date adds a fraction of the day, and that fraction is counted from noon UTC, because astronomers wanted a whole night's observing to fall on one number. So midnight UTC opening 1 January 2000 is JD 2451544.5, and if you type a Julian Date with a fraction the converter rounds it to the day it falls in and says so.
What is the Modified Julian Date?: The Julian Date minus 2400000.5. The half day moves the start of the day to midnight, and the 2400000 drops two digits, so a date this century is a five-digit number: 1 January 2000 is MJD 51544 and 2 September 2026 is MJD 61285. MJD 0 is 17 November 1858. It is used in satellite tracking, space telemetry and time-signal work. Pick MJD next to the field in JDN mode to type one directly, or read it from the list for any date.
What is today's Julian date?: The page opens on today, read from your device's own calendar, so the two large numbers at the top are today's ordinal stamp and today's Julian Day Number. The Today button brings any other date back to it. The date is read from your calendar rather than the UTC instant, so it is the day on your wall rather than the day in Greenwich, which is already tomorrow for part of the world every evening.
How do I convert between the Julian and Gregorian calendars?: Select Julian calendar, then Gregorian to Julian or Julian to Gregorian. Gregorian dates use the date picker. Type an old Julian calendar date as YYYY-MM-DD, including a Julian leap day such as 1900-02-29. That date becomes Gregorian 1900-03-13. Julian years divisible by four are leap years; Gregorian century years also need to be divisible by 400. The offset therefore changes over the centuries rather than staying at 13 days.
Does this convert historical dates using a country's calendar changeover?: Both calendars are applied throughout the supported range. No country-specific adoption date is used. Julian 1582-10-05 converts to Gregorian 1582-10-15, but dates around a local calendar changeover require knowing which calendar the record used.
Can I use military or egg-packaging Julian codes here?: For a day-of-year code, choose Ordinal to date. A bare three-digit day uses the current year, and YYDDD includes a two-digit year. The conversion identifies a calendar day; it does not determine shelf life, an expiration date or whether an item is safe to use. Manufacturer-specific codes and JD Edwards CYYDDD fields are not decoded.
Can I convert a date from 2024, 2025 or 2026?: Use the Date field to choose the year you need. Gregorian 2024 is a leap year with 366 days; 2025 and 2026 have 365. Today always means the current date from your device, even when an older year appears in a question.
Can I use this in a phone or desktop browser?: The converter runs in your browser. Use the date picker, or type a code into its labelled field. No account or upload is needed.
Does it calculate the Julian Date for a specific time?: The output lists Julian Date at midnight UTC for the chosen date. A fractional JD or MJD can be entered in JDN to date mode to identify its calendar day, but the result does not preserve the time of day. Heliocentric and barycentric corrections are not calculated.
What formula converts a Gregorian date to a Julian Day Number?: Using year Y, month M and day D, first set A = floor((14 - M) / 12), y = Y + 4800 - A and m = M + 12A - 3. Then JDN = D + floor((153m + 2) / 5) + 365y + floor(y / 4) - floor(y / 100) + floor(y / 400) - 32045. The Julian Date at midnight UTC is JDN - 0.5. An ordinal day number instead counts from 1 January in the same Gregorian year.
What date is Julian day 212 in 2026?: For the day-of-year meaning, day 212 of 2026 is 31 July. Its five-digit stamp is 26212 and its seven-digit stamp is 2026212. This is different from astronomical Julian Day Number 212, which falls outside the supported calendar range.

Exact. The ordinal date counts days from 1 January, and the Julian Day Number uses the standard Gregorian algorithm; both are checked against known dates in the tests.