I'm inventing a new calendar:

  • It will be used worldwide.
  • It uses an intercalary (366th) day to be inserted every 4 years.
  • If extremely successful (unlikely I know), it will replace the Gregorian calendar not earlier than in a century.
  • Its associated set of units of measurement (length, mass, etc.) is based on natural units.

What are good criteria for the choice of the first day?

Some possibilities:

  • January 3 periapsis
  • July 3 apoapsis
  • March 20 equinox
  • June 21 solstice
  • September 22 equinox
  • December 21 solstice
  • 1 October, the beginning of the dry season (meteorological Tropical season)
  • 1 April, the beginning of the wet season (meteorological Tropical season)

What are good criteria for the choice of the first year?

Ideally I would have wanted to pick the year of the Big Bang but even in a century it will never be known with precision.

What are good criteria for the choice of the first hour of the day? The possibilities: the days can start at midnight, sunrise, noon or sunset.

  • $\begingroup$ This seems too broad, you’re asking several different questions here instead of one specific question. This also seems opinion based, how are you going to judge the best answer? Any answer seems like it would be equally valid. $\endgroup$ Jun 7, 2019 at 14:07
  • $\begingroup$ Now, because why not? Even modern calendars have 3 new years, calendar, tax, school. Everything else is entirely arbitrary. $\endgroup$
    – Separatrix
    Jun 7, 2019 at 14:08
  • 1
    $\begingroup$ I agree with @LiamMorris. While I think this kind of question encourages creativity, it will likely be voted by some as opinion-based. You might want to add some criteria for elegibility of the best answer(s), and possibly make it separate questions $\endgroup$
    – Rafael
    Jun 7, 2019 at 14:11
  • $\begingroup$ How would this be different than using Julian days for calculations (besides an earlier epoch) or else why not use Julian and just change the epoch? $\endgroup$
    – LinkBerest
    Jun 7, 2019 at 14:11
  • 1
    $\begingroup$ OK. I edited my question. I believe it isn't opinion-based anymore. $\endgroup$ Jun 7, 2019 at 14:46


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