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Julian day decoder

World's simplest time tool

With this browser-based application, you can decode a Julian day (JD) or a Julian day number (JDN) to a regular calendar date that humans can instantly understand. You can enter one or several JDs/JDNs into the input area and get an understandable Gregorian date (modern calendar date) or a Julian date (old calendar date) as the output. You can also customize the date and time format and create custom date format templates. Created by computer nerds from team Browserling.
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Output Calendar
Convert a Julian day to a date in the Gregorian calendar.
Convert a Julian day to a date in the Julian calendar.
Output Calendar Format
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
• YYYY/YY – year, • MMMM/MMM/MM – month, • dddd/ddd – day of week, • DD – day, • hh – hour, • mm – minute, • ss – second.
Extra Format Options
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
Julian day decoder tool What is a julian day decoder?
This is a quick online utility for finding a calendar date by the Julian day or Julian day number. Each calendar date and time has its own unique numeric value, called a Julian day (abbreviated as "JD"). This number is a continuous count of days since the beginning of the Julian period, which is defined as the noon of January 1, 4713 BC in the Julian calendar (and the noon of November 24, 4714 BC in the Gregorian calendar). Note that there are two very similar concepts – a Julian day and a Julian date. They often get confused and they are not the same. The Julian day is a number but the Julian date is a date in the Julian calendar. As of this moment, the Julian day is already above 2,459,714. Our astronomical algorithm converts any Julian day value to the exact Gregorian or Julian calendar date and time. In the options, you can select which calendar to use – either Gregorian or Julian. For example, entering a JD equal to "2459587.25" as the input will produce the Gregorian date "2022-01-07 6:00:00 pm" as the output. Similarly, the same JD will produce the Julian date "2021-12-25 6:00:00 pm" as the output. You can enter multiple JDs into the input, one per line, and get multiple readable dates in the output. You can also customize the output date format and create completely custom calendar formats by switching to the custom format mode. In this mode, you can use abbreviations such as MM, DD, and YYYY to create unique date templates. You can also add zero padding for date and time parts and switch between 24-hour and 12-hour clock formats. If you need to perform the reverse calculation, which is finding the Julian day from a Gregorian or Julian date, you can use our Convert a date to a Julian day tool. Timeabulous!
Julian day decoder examples Click to use
Julian Day of Sputnik 1 Launch
In this example, we found a reference to the Julian day 2436116.3115 in an astronomy textbook. To understand the event behind this number, we turned this Julian day into a date from the Gregorian calendar. We got the date "1957-10-04 19:28:34" and found out that this is the launch date of the Sputnik 1 satellite.
2436116.3115
1957-10-04 19:28:34
Required options
These options will be used automatically if you select this example.
Convert a Julian day to a date in the Gregorian calendar.
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
Julian Days to Julian Dates
In this example, we convert four Julian days into Julian dates. All input Julian days don't have a fractional part of the date, which means that they correspond to the noon of the dates. JD = 0 becomes the year -4712, JD = 1000000 corresponds to the year -1975, JD = 2000000 decodes to the year 763, and JD = 2460000 converts to the year 2023. We select a date output format with abbreviated months, remove the padding, and turn the time into a 12-hour format. Also, a quick note – a Julian day without a fractional/decimal part is called a Julian day number (JDN).
0 1000000 2000000 2460000
-4712, 1 Jan 12:0:0 pm -1975, 7 Nov 12:0:0 pm 763, 14 Sep 12:0:0 pm 2023, 11 Feb 12:0:0 pm
Required options
These options will be used automatically if you select this example.
Convert a Julian day to a date in the Julian calendar.
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
Decode a Julian Day Number
In this example, we decode a spiral list of pretty Julian day numbers (JDNs) consisting of the digits "2" and "4". We ignore the clock time part and turn these JDNs into custom-formatted Gregorian dates. To do it, we switch to the custom mode in the output date format list and then enter the output date pattern equal to "ddd, DD-MMM-YYYY" in the custom date pattern field.
2222224 2222242 2222422 2224222 2242222 2422222 4222222
Fri, 21-Feb-1372 Tue, 10-Mar-1372 Sun, 06-Sep-1372 Mon, 11-Aug-1377 Thu, 23-Nov-1426 Sat, 20-Sep-1919 Fri, 13-Dec-6847
Required options
These options will be used automatically if you select this example.
Convert a Julian day to a date in the Gregorian calendar.
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
Interesting Julian Days
This example decodes several interesting round JDs into readable human calendars. One of the most interesting JDs is 2500000, which is the closest round number to today's JD (which is 2459715). The JD 2500000 will happen on 2132-08-17.
1 10 100 500 1000 5000 10000 50000 100000 500000 1000000 2500000 5000000 10000000 50000000 100000000
-4713-11-25 -4713-12-04 -4712-03-03 -4711-04-07 -4710-08-20 -4699-08-03 -4685-04-12 -4576-10-17 -4439-09-09 -3344-11-07 -1975-10-21 2132-08-31 8977-06-07 22666-12-20 132183-04-01 269078-08-07
Required options
These options will be used automatically if you select this example.
Convert a Julian day to a date in the Gregorian calendar.
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
Binary JDs
In this example, we let our crazy astronomer friend who loves binary numbers play with our utility. The first thing he did is try it out on JDs which consist only of 1's and 0's, including the decimal part. These are the results he got.
1.00 1.01 1.10 1.11 11.11 111.111 1111.1111 10101010.10101010
-11/25/4713 12:00:00 pm -11/25/4713 12:14:24 pm -11/25/4713 02:24:00 pm -11/25/4713 02:38:24 pm -12/05/4713 02:38:24 pm -03/14/4712 02:39:50 pm -12/09/4710 02:39:59 pm 07/11/22943 02:25:27 pm
Required options
These options will be used automatically if you select this example.
Convert a Julian day to a date in the Gregorian calendar.
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
21st Century Julian Days
This example shows the Julian days of the 21st century. They include the JDs from the year 2000 to the year 2099.
2451545 2451546 2451575 2458850 2459216 2459581 2459946 2460311 2460677 2461042 2461407 2461772 2462138 2462503 2487705 2487735
2000/01/01 2000/01/02 2000/01/31 2020/01/01 2021/01/01 2022/01/01 2023/01/01 2024/01/01 2025/01/01 2026/01/01 2027/01/01 2028/01/01 2029/01/01 2030/01/01 2099/01/01 2099/01/31
Required options
These options will be used automatically if you select this example.
Convert a Julian day to a date in the Gregorian calendar.
Select the format for the output calendar date.
Use abbreviations to create a custom date format. (Valid when the custom format option is active.)
Add zeros to the date and time components to get full-width dates.
Switch all output time parts to a 12-hour format.
Pro tips Master online time tools
You can pass input to this tool via ?input query argument and it will automatically compute output. Here's how to type it in your browser's address bar. Click to try!
https://onlinetimetools.com/convert-julian-day-to-date?input=2436116.3115&to-gregorian-date=true&format=YYYY-MM-DD%20hh%3Amm%3Ass&custom-format=YYYY_MM_DD&padding=true&use-12-hour-clock=false
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