pub fn serial_from_ymd(
sys: DateSystem,
year: i64,
month: i64,
day: i64,
) -> Option<f64>Expand description
Serial for a date. Month and day overflow roll over like DATE() (month 13 = January next
year, day 0 = last day of the previous month), in the date system’s own calendar: in the 1900
system February 1900 has 29 days, so (1900, 2, 29) and (1900, 3, 0) are serial 60.
None before the epoch or after 9999-12-31.