Auxiliary Time functions

Five auxiliary functions are provided for working with Times. These have all been defined as static members of class Time to avoid polluting the global namespace.

• Time::is_leap() tells whether a given year is a leap year:

         Time::is_leap(1987)  // returns 0
         Time::is_leap(1988)  // returns 1
  

• Time::days_in_year() tells the number of days in a given year:

         Time::days_in_year(1987) // returns 365
         Time::days_in_year(1988) // returns 366
  

• Time::days_in_month() returns the number of days in a given month of a given year (the only annual variation in the function result is for February):

         Time::days_in_month(Time::february,1988)
           // returns 29
  

• Time::first_day() returns the Julian day number of the first day of a given month in a given year:

         Time::first_day(Time::february,1988)
           // returns 32
  

• Time::valid_date() takes a date specified as (year, month, day) and returns 1 if the parameters describe a valid date and 0 otherwise:

         Time::valid_date(1988,Time::february,29)
           // returns 1
         Time::valid_date(1989,Time::february,29)
           // returns 0
  

  For an example that uses Time::valid_date(), see ``Constructors'' section.