Months and days are numbered according to the Gregorian calendar.
It was used in mainland China from 1912 until the founding of the People's Republic of China in 1949.
They help confirm the Start and End numbers or indicate the range where the Start and End numbers are unknown.
I don't receive information from Nikon or sponsorship from any other business, this list has been put together from many years of independent research and from details forwarded by readers.
Easter Day was celebrated either: (a) on or just after the first day of the Jewish Passover (no matter on which day of the week that Easter Day occurred), or (b) on a Sunday close to or on the first Passover Day. Precise information on this subject can be found on pages 415 to 425 of the Explanatory Supplement to the 1961 Astronomical Ephemeris.
It became defined as the Sunday following the Paschal Full Moon date for the year, using a simple "19 PFM dates" table.