Parse a YYYY, YYYY.MM, or YYYY.MM.DD spec into its inclusive [lower, upper] millisecond window (the whole year / month / day named), or undefined when malformed or out of range (month 1..12, day 1..31).
YYYY
YYYY.MM
YYYY.MM.DD
[lower, upper]
undefined
1..12
1..31
Parse a
YYYY,YYYY.MM, orYYYY.MM.DDspec into its inclusive[lower, upper]millisecond window (the whole year / month / day named), orundefinedwhen malformed or out of range (month1..12, day1..31).