Comment: LOL....I hear ya... :)

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LOL....I hear ya... :)

The Gregorian calendar tries to keep the spring equinox at March 21 (+/- a day or two). It uses fixed rules, and is accurate to about 1 day in 2000 years.

The Persian (Solar Hejri) calendar is a observational calendar. It does not use fixed rules like most other calendars. In that sense, it is most "accurate". But it requires consulting an astronomical almanac, and it is impossible to say how long the year will be for more than 1000 years in advance. And maybe even less than that, whenever the vernal equinox happens close to noon. (What would happen if one person said the equinox happened 0.1 second before noon, and another person said it was 0.1 second after noon?) So the Persian calendar is no more accurate than our predictions of the orbit, inclination, and rotation of the Earth. And those predictions are basically good to only +/- 1 second for the next 25 years (especially for Earth rotation).

The Hebrew calendar doesn't even try to match the solar cycle. It is 100% accurate in following it's own rules, which is all it tries to do. There has been some discussion about a need to change the rules, sometime in the next 5000 years or so.

There are many Hindu calendars. Most all the variations are observational calendars, so they are 100% accurate as far as people can see the sun and moon (or use almanacs). But again, they have the problem of the equinox happening very near a time point -- in this case, sunrise.

The Mayan calendar used 365 days a year, every year. The pre-Colombian Mayans knew this was not accurate in tracking the seasons, but they used it anyway.

The most accurate calendar in all senses is the Julian Day (JD) calendar. It is just a count of the days since January 1, 4713 BC Greenwich noon. This calendar is used by the astronomical community.