Post

So big blocker to calendar reform is breaking 7 day cycle for day of worship 'keep the sabbath day holy.' Commandment number 4. Kinda a biggie. Reform for 364+1 calendars would need buy in from Jewish, Christian, & Muslim groups. en.wikipedia.org/wiki/World_C...

Dave DeSandro

@desandro.com

Hanke–Henry Permanent Calendar maintains 7 day cycle by using leap _weeks_ instead of leap days. There's also Symmetry454 calendar, which has months of either 28 or 35 days. I like the work around, but solar misalignment feels like a big compromise en.wikipedia.org/wiki/Hanke%E...

en.wikipedia.orgHanke–Henry Permanent Calendar - Wikipedia

24/8/26, 4:53 pm0 reposts2 likes

Calendar Design and Reform

@calendar-reform.bsky.social

28 Aug

Irv Bromberg actually tries to minimize that effect by adopting a smooth leap rule over a 293y cycle for his #SymmetryCalendar. More practically, #HHPC keeps using the rules suggested by ISO 8601-1, which adds a leap week based on the Gregorian olympiad-centennial leap-day rule over its 400y cycle.

Calendar Design and Reform

@calendar-reform.bsky.social

28 Aug

The alternative, direct 5:40:400 leap-week rule would hardly be any better astronomically than the indirect ISO one depending on the 4:100:400 leap-day rule. It is regular, though, and would therefore be more practical and user-friendly.

calendars.fandom.com400-year leap cycleA leap cycle of 400 years contains 97 leap days or 71 leap weeks and thus overall 146097 days and 20871 weeks or 4800 twelfth-of-a-year months, spanning roughly 4947.3 lunations. Its mean year length ...