How to read Julian date – Julian calendar converter

How to read Julian date

The Julian calendar counts years, months, and days from January 1, 4713 BCE. The Julian date, on the other hand, is a continuous count of days since noon UTC on January 1, 4713 BCE. To read a Julian date, you typically represent it as a whole number with no decimal places. For example, Julian date, 2459589, corresponds to February 15, 2023, in the Gregorian calendar.

Convert a Julian date to a Gregorian calendar date

You can use a conversion formula if you want to convert a Julian date to a Gregorian calendar date. Here is a simple algorithm to convert a Julian date to a Gregorian date:

1. Subtract 1721424.5 from the Julian date.
2. Divide the result by 365.25 to get the number of years (including fractional years) since January 1, 4713 BC.
3. Take the integer part of the number of years to get the year.
4. Multiply the fractional part of the number of years by 365.25 to get the number of days into the current year.
5. Add 0.5 to the number of days into the current year.
6. Convert the result to a Gregorian date using a calendar algorithm.

Note that there are several different algorithms for converting Julian dates to Gregorian dates, and the conversion details may vary depending on the algorithm used.

Example:

Let’s say we have a Julian date of 2459589. To convert this to a Gregorian date, we can use the algorithm I described earlier:

1. Subtract 1721424.5 from the Julian date: 2459589 – 1721424.5 = 738164.5
2. Divide the result by 365.25: 738164.5 / 365.25 = 2019.99826
3. Take the integer part of the number of years to get the year: 2019
4. Multiply the fractional part of the number of years by 365.25 to get the number of days into the current year: 0.99826 * 365.25 = 364.625215
5. Add 0.5 to the number of days into the current year: 364.625215 + 0.5 = 365.125215
6. Convert the result to a Gregorian date using a calendar algorithm. In this case, the date would be February 15, 2023.

So the Julian date 2459589 corresponds to February 15, 2023, in the Gregorian calendar.

Convert a Gregorian calendar date to a Julian date

To convert a Gregorian calendar date to a Julian date, you can use the following algorithm:

1. Count the days between the given date and January 1 of the year 4713 BC in the Julian calendar.
2. Add 1721424.5 to the result.

Example:

Here is an example of how to convert the Gregorian date, February 15, 2023 to a Julian date:

1. Count the days between February 15, 2023, and January 1, 4713 BC, in the Julian calendar. We can do this by adding up the number of days in all the years from 4713 BC to 2022 AD and then adding the number of days from January 1 to February 14 in 2023. Here’s the calculation:4712 years * 365.25 days per year = 1726218 days 2022 years * 365.2425 days per year = 738035.5 days January 1 to February 14, 2023 = 44 daysTotal = 1726218 + 738035.5 + 44 = 2460297.5
2. Add 1721424.5 to the result:2460297.5 + 1721424.5 = 4181722

So the Gregorian date, February 15, 2023, corresponds to Julian’s 4181722.