Classication of Calendars
Gregorian calendar. Basic unit is day. Approximates the tropical year by
adding leap days. Ignores the Moon.
Islamic calendar. Basic unit is lunar month. Ignores the Sun.
Chinese and Jewish calendars. Basic unit is lunar month. Approximates the
tropical year by adding leap months.
The Chinese calendar is NOT a lunar calendar!
Alternative Classication of Calendars
Gregorian, Indian and Jewish calendars. Based on arithmetical
formulas. Prediction and conversion between different
arithmetical calendars is simple.
Islamic, Indian and Chinese calendars. Based on astronomical
data. Prediction and conversion is hard.