Overview#Day is defined in RFC 3339 as a period of time of 24 hours
Besides the day of 24 hours (86,400 seconds), the word day is used for several different spans of time based on the rotation of the Earth around its axis. An important one is the solar day, defined as the time it takes for the Sun to return to its culmination point (its highest point in the sky). Because the Earth orbits the Sun elliptically as the Earth spins on an inclined axis, this period can be up to 7.9 seconds more than (or less than) 24 hours.
More Information#There might be more information for this subject on one of the following:
- DirXML Code Snippets
- Leap year
- Time And Epochs