How it works
ISO ordinal date = four-digit Gregorian year followed by the three-digit 1-based day of year.
Input definitions
- Gregorian calendar date
- A complete Gregorian calendar date.
A worked example
- Gregorian calendar date
- 2024-02-29
Assumptions & limits
Gregorian years 0001–9999. Uses UTC calendar midnights; local daylight-saving changes do not affect the day-of-year count.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Is an ordinal date the same as a Julian date?
No. This output is a year and 1-based day number, such as 2024-060. Astronomical Julian day numbers count days continuously from a different epoch.
Do daylight-saving changes affect calendar date results?
Date-only operations compare Gregorian calendar dates at UTC midnight. They do not count local elapsed hours. Timestamp operations require an explicit offset; individual tool assumptions state boundary rules.
How does the Calendar date to ISO ordinal date tool work?
ISO ordinal date = four-digit Gregorian year followed by the three-digit 1-based day of year.
What are the assumptions and limits of Calendar date to ISO ordinal date?
Gregorian years 0001–9999. Uses UTC calendar midnights; local daylight-saving changes do not affect the day-of-year count.