Created attachment 109385 [details] Results provided by IMCCE (https://promenade.imcce.fr/en/pages4/439.html) vs provided by Kstars The dates of the equinoxes and solstices given in kstars by the calculator tool are wrong. 1- It seems that there is a lag of one year. 2018 in kstars => 2017 for the IMCCE (Institute for Celestial Mechanics and Computation of Ephemerides, official service that "manages" the time in France, see presentation here : https://www.imcce.fr/institut/presentation/) 2 even with the lag of a year, there are differences of several minutes between the different results.
I was checking against other online sources for 2017 and the results are pretty close with few minutes of difference only.
The winter solstice in 2017 is scheduled for December 21 at 16:29 UTC (or 16:27 according to the IMCCE). What I do not understand is why Kstars tells me that it is scheduled for December 21 at 22:19 UTC? I tested kstars on two different computers.
Confirming. For 2018, they are even more wrong. On my system, it lists: Vernal equinox: 20 March 2018 22:18:23 UTC Summer solstice: 21 June 2018 16:41:01 UTC Autumnal equinox: 23 September 2018 08:12:20 UTC Winter solstice: 22 December 2018 04:18:47 UTC While https://www.timeanddate.com/calendar/seasons.html?n=1440 lists Vernal equinox: 20 March 2018 16:15 UTC Summer solstice: 21 June 2018 10:07 UTC Autumnal equinox: 23 September 01:54 UTC Winter solstice: 21 December 2018 22:22 UTC (Note that also the *date* for the winter solstice differ.) The U.S. Naval Observatory lists similar dates/times at http://aa.usno.navy.mil/seasons?year=2018&tz=0&tz_sign=-1 (For winter solstice, they list the time as 22:23 instead of 22:22. Perhaps different rounding rules?)
Git commit de594e589673f281357051a59c076c8cbd3cb30a by Jasem Mutlaq. Committed on 18/02/2020 at 09:03. Pushed by mutlaqja into branch 'master'. Fixed Equinox and Solstice dates in Calculator Summary: This patch uses a revised version of the algorithm from Astronomical algorithms - Jean Meeus to calculate the correct dates of Equinox and Solstice in Calculator. Reviewers: mutlaqja Reviewed By: mutlaqja Subscribers: mutlaqja, kde-edu Tags: #kstars, #kde_edu Differential Revision: https://phabricator.kde.org/D27413 M +142 -97 kstars/tools/modcalcvizequinox.cpp M +2 -2 kstars/tools/modcalcvizequinox.h https://commits.kde.org/kstars/de594e589673f281357051a59c076c8cbd3cb30a