Calendar

Calendar Date

Day is an opaque Int value, holding day index since start of 1970

 // Find all Fridays the 13th for this century
 (2000 <>> 2100).stream.map(_.Year).flatMap(_.days)
    .take(d => d.number == 13 && d.weekDay.isFri)
    .peek(_.tp)
    .count.self("Total Count: " + _ tp())

 // Output
 2001-04-13
 2001-07-13
 . . . . .
 2099-11-13
 Total Count: 172

Calendar Month

Month is an opaque Int value, holding month index since start of 1970

Calendar Week

Week is an opaque Int value, holding week index since start of 1970

Calendar Year

Year is an opaque Int value, holding literally the year number