Free Julian Date Calculator
Convert a UTC Gregorian date and time into Julian Date, Modified Julian Date and day-of-year values.
Julian Date Calculator
Enter a value to begin.
How to use this julian date calculator
- Enter a UTC date and time from 1801 through 2099, then calculate the three day-number forms.
- Check the inputs and preview, then use the primary action.
- Download, copy or use the result shown by the tool.
How the result is calculated
Julian Date is the continuous astronomical day count whose integer boundary occurs at noon. Modified Julian Date equals JD minus 2,400,000.5 and begins at midnight; day of year is the ordinary ordinal day within the entered Gregorian year.
Read the current U.S. Naval Observatory Julian Date definition and conversion guidance before submitting.
All calculation and transformation work happens in this browser tab. No entered value is sent to an Noler Tools application server.
Important limitations
Results are provided for convenience and should be checked independently before an important decision. A format or checksum result never authenticates an identity, document, account, licence, vehicle or registration.
Frequently asked questions
Is this julian date calculator free?
Yes. It is free to use and does not require an account.
Does Noler Tools save my input?
No. The input and result remain in temporary browser memory and are not uploaded or saved by this site.