Help and Information to the everlasting calendar

Help and Characteristics

  • If the entry of the current date in the form and the calendar output don't happen automatically, simply click in the form on <<heute>> .
    Any date (day, month and year, alternatively Julian day) can be entered. The button <<show! >> computes the two-monthly calendar as well as information to the current day, holidays, moon etc..
    <<today>> does the same for the actual period.
  • For the computation of time intervals or a target date there is a time computer. Nevertheless the Julian date is suitable. One can copy and paste e.g. into the Windows calculator.
  • The feast calculator computes, in which years a selected holiday falls on a certain date.
  • Years with the same weekday sequence and dates in the pregnancy can be computed as well.
  • There are print versions of several calendar layouts such as yearly calendar, monthly calendar, 3 month calendar.
  • the letters will fall down by pressing a mouse button or doubleclicking. Moving the pointer to the edge, the animation disappears.


The program computes calendar dates up to 1582/10/4 in the Julian calendar, starting from 1582/10/15 in the Gregorian calendar, which ends in the year 4099 [… rather rather]. Extrapolation into the past does not require a historical basis. The days in between were cancelled within the calendar reform. For the calendar reform the dating of the Vernal equinox on march 21 was determining.
I optimized the astronomical algorithms for the computation of moon and seasons for a little, so that errors are not to be excluded from up to 7 minutes at 200 years difference (15 min. at 400 years), not at least by the transformation in world time (UT). For Central Standard Time (CST) subtract 6 hours from UTC.
Sunrise and sunset refer to the upper sun edge and consider the atmospheric refraction. The deviation amounts up to 2 minutes. The daylight saving time is not considered.

The computation of the Easter date is a direct conversion of the valid rule and should fit without exception in every year > 325. The results agree in the years 1 to 4099 with the Gauss Easter formula, which can be found in their obviously complete version at Dietrich Kracht. One notes however that e.g. some south European countries depend on the Easter date of the orthodox churches. Further information in addition as well as various program translations provides GM Arts.
The feasts and their origins were conscientiously investigated, however I cannot put my hand in the fire for all data provided here, particularly since in the program consideres the current rules.

By the use of completely independent algorithms the program is carefully tested. Nevertheless are
all data like everywhere without guarantee!

Copyright © 1998-2007 Thomas's Köhler, All rights reserved.

… up to the beetle picture (entirely stolen of the "Tagesspiegel" which linked this program (to 00/3/26, topic time conversion) to nice way)

The program: everlasting calendar