sclass DateStructures {

  asclass SomeDate {}

  asclass SomeDateDate > SomeDate {} // day or higher granularity

  asclass SomeTime > SomeDate {}

  asclass SomeWeek > SomeDateDate {}

  asclass DateProp > SomeDate {} // proposition on a date, e.g. a date range

  // years

  static transformable record Year(int year) > SomeDateDate {}

  static transformable record CurrentYearPlus(int nYears) > SomeDateDate {}

  // months

  static transformable record Month(int month, Year year) > SomeDateDate {

    Month(int month) { this(month, null); }

  }

  static transformable record CurrentMonthPlus(int nMonths) > SomeDateDate {}

  // weeks

  static transformable record Week(int week, Year year) > SomeWeek {}

  static transformable record CurrentWeekPlus(int nWeeks) > SomeWeek {}

  // days

  static transformable record Day(int day, Month month) > SomeDate {}

  static transformable record TodayPlus(int nDays) > SomeDate {}

  // weekdays

  static transformable record Weekday(int weekday, SomeWeek week) > SomeDateDate {

    // weekday is in Java count (1=Sunday)

    Weekday(int weekday) { this.weekday = weekday; }

  }

  // hours

  static transformable record Hour(int hour, Bool isPM, Day day) > SomeTime {

    Hour(int hour, Bool isPM) { this(hour, isPM, null); }

  }

  static transformable record CurrentHourPlus(int nHours) > SomeTime {}

  // minutes

  static transformable record Minute(int minute, Hour hour) > SomeTime {}

  static transformable record CurrentMinutePlus(int nMinutes) > SomeTime {}

  // seconds

  static transformable record Second(int second, Minute minute) > SomeTime {}

  // special stuff

  static transformable record BeginningOfTime > SomeDate {}

  static transformable record EndOfTime > SomeDate {}

  // date ranges & boolean operations

  static transformable record Between(SomeDate from, SomeDate to) > DateProp {}

  static transformable record Or(DateProp a, DateProp b) > DateProp {}

  static transformable record And(DateProp a, DateProp b) > DateProp {}

  static transformable record Not(DateProp a) > DateProp {}

  // some utility functions

  sbool containsTimes(SomeDate d) {

    ret defaultMetaTransformer().any(o -> o instanceof SomeTime, d);

  }

  sbool containsDateDates(SomeDate d) {

    ret defaultMetaTransformer().any(o -> o instanceof SomeDateDate, d);

  }

}