Symmetry Calendar Date Conversion Sheets

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The following quick reference calendar date conversion sheets list information that is useful for manually converting other widely-used calendars to Symmetry454 or Symmetry010 dates, thus avoiding the use of a computer for simple conversions.

Symmetry454 (4+5+4 weeks per quarter)

Symmetry010 (30+31+30 days per quarter)

Each report title gives the name of the calendar (Symmetry454 or Symmetry010) and the year number.

The next line states the calendar options as configured in Kalendis at the time that the report was generated, followed by the leap rule description.

The line that begins with "Sym-Greg month:" gives the number of days to add to the Gregorian date to convert it to the Symmetry date. For example, for 2008 the Symmetry454 report lists -2 for March, so Gregorian March 15 converts to Symmetry454 March 15-2=13. It lists +5 for November, so Gregorian November 12 converts to Symmetry454 November 12+5=17. This works well within months, but can get tricky near the beginning or end of a month. Therefore the report also tabulates the start and end of each Symmetry454 or Symmetry010 month, showing:

The year 2009 was a Symmetry leap year, and was also be a Chinese leap year (indicated by an asterisk * between month and day in the Chinese date column). For the Symmetry leap year two formats are posted: leap week appended to December, or leap week stand-alone at the end of year.

It isn't possible to make a perpetually re-usable sheet or set of sheets, because the Symmetry 52/293 leap rule (calendar mean year of 365+71/293 days) doesn't maintain a fixed relationship to other calendars. Calendars that have identical mean years never drift apart.

If the user selected the ISO leap rule as an "experimental" option in Kalendis then the Symmetry date would have a drift-free relationship to the Gregorian, ISO, and Western Bahá'í calendars, with a calendar mean year of 365+97/400 days. In this case there would be 14 possible annual patterns: 7 for each Gregorian year weekday start of non-leap and leap Gregorian year types.

This page updated Feb 19, 2011 (Symmetry454) = Feb 17, 2011 (Symmetry010) = Feb 18, 2011 (Gregorian)