Constructs a YearMonth from a year and month, a Date, a YearMonthDay, or a YearQuarter with an optional period assumption.
auto ym1 = YearMonth(YearQuarter(2000, Quarter.q1)); auto ym2 = YearMonth(YearQuarter(2000, Quarter.q1), AssumePeriod.end);
Constructs a YearMonth from a year and month, a Date, a YearMonthDay, or a YearQuarter with an optional period assumption.