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.

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

The default handling of the leap week for Symmetry454 is to append it to December, but for Symmetry010 by default it stands alone after December.

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 abbreviated weekday name, which applies to all calendars on the report.
• The ordinal week number within the Sym454 or Sym010 calendar year, and the day number within the week (1=starting weekday as indicated in the second line at the top of the report, normally Monday unless the Kalendis user selected an experimental alternative).
• The ISO date, showing the week number within the ISO calendar year, and the day number within the week (1=Monday).
• The ordinal day number within the Sym454 or Sym010 calendar year.
• The ordinal day number within the Gregorian calendar year.
• The Sym454 or Sym010 date, showing the abbreviated month name and the day in that month.
• The Gregorian date, showing the abbreviated month name and the day in that month.
• Optionally, if its window was open at report generation time, the Julian or Revised Julian date, showing the abbreviated month name and the day in that month. (These examples use the Julian date because currently the Revised Julian date is the same as the Gregorian date.)
• Optionally, if its window was open at report generation time, an oriental traditional lunisolar calendar month-day. This column can show the Chinese, Korean, Vietnamese, or Japanese date, depending on which calendar type was selected in the oriental calendar window in Kalendis. The lunisolar leap month is indicated by an asterisk * between month and day in the oriental date column.

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 from the build-in experimental options in Kalendis then the Symmetry date would have a drift-free relationship to the Gregorian and ISO calendars, with a calendar mean year of 365+⁹⁷/₄₀₀ days. In this case there would be only 14 possible annual patterns: 7 for each Gregorian year weekday start of non-leap and leap Gregorian year types.

This page updated Dec 16, 2017 (Symmetry454) = Dec 18, 2017 (Symmetry010) = Dec 19, 2017 (Gregorian)