ETC constructor
Construct an ETC instance.
For example. to create a new ETC object representing the 1st of ጷጉሜን 2011,
var etc = ETC(year: 2011, month: 13, day: 1);
Month and day are optional, if not provided ETC will assume the first day of the first month of the given year.
Implementation
ETC({required int year, int month = 1, int day = 1})
: _date = EtDatetime(year: year, month: month, day: day);