The Equation of Time is the difference between the time determined by a sundial and the clock time. It is due to the obliquity of the Earth's axis and the unequal motion of the Earth (ellipse). The value, computed for 12:00 UT, is between -14 :20 min (near Feb 12) and +16:24 min (near Nov 4). The length of the current solar day (i.e. the time interval between culmination of the Sun on prev. and curent day) is not exactly 24 hours; the difference is given in brackets (e.g. +18.8 s).

Equation of time and length of solar day:
(for 2001)

	equation of time	length of solar day
Jan 1	- 03:45 min	24 h - 28.3 s
15	- 09:34 min	24 h - 21.2 s
Feb 1	- 13:38 min	24 h - 08.1 s
15	- 14:07 min	24 h + 02.8 s
Mar 1	- 12:18 min	24 h + 11.6 s
15	- 08:51 min	24 h + 16.8 s
Apr 1	- 03:48 min	24 h + 17.9 s
15	+ 00:02 min	24 h + 14.6 s
May 1	+ 02:57 min	24 h + 07.3 s
15	+ 03:40 min	24 h - 00.6 s
Jun 1	+ 02:09 min	24 h - 09.1 s
15	- 00:31 min	24 h - 12.8 s
Jul 1	- 03:53 min	24 h - 11.6 s
15	- 05:59 min	24 h - 06.2 s
Aug 1	- 06:18 min	24 h + 03.6 s
15	- 04:24 min	24 h + 11.7 s
Sep 1	+ 00:06 min	24 h + 18.9 s
15	+ 04:55 min	24 h + 21.4 s
Oct 1	+ 10:26 min	24 h + 19.4 s
15	+ 14:17 min	24 h + 13.4 s
Nov 1	+ 16:24 min	24 h + 01.7 s
15	+ 15:20 min	24 h - 10.0 s
Dec 1	+ 10:50 min	24 h - 22.3 s
15	+ 04:41 min	24 h - 28.8 s

Equation of Time

Length of Solar Day

Web Links

Equation of Time (Royal Greenwich Observatory Information Leaflet) Sundials on the Internet - the Equation of Time Equation of Time -- Problem in Astronomy (M. Müller)