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Function std.datetime.date.DateTime.diffMonths

Returns the difference between the two DateTimes in months.

int diffMonths (
  const(DateTime) rhs
) pure nothrow @nogc @safe const;

To get the difference in years, subtract the year property of two DateTimes. To get the difference in days or weeks, subtract the DateTimes themselves and use the Duration that results. Because converting between months and smaller units requires a specific date (which Durations don't have), getting the difference in months requires some math using both the year and month properties, so this is a convenience function for getting the difference in months.

Note that the number of days in the months or how far into the month either date is is irrelevant. It is the difference in the month property combined with the difference in years * 12. So, for instance, December 31st and January 1st are one month apart just as December 1st and January 31st are one month apart.

Parameters

NameDescription
rhs The DateTime to subtract from this one.

Example

assert(DateTime(1999, 2, 1, 12, 2, 3).diffMonths(
           DateTime(1999, 1, 31, 23, 59, 59)) == 1);

assert(DateTime(1999, 1, 31, 0, 0, 0).diffMonths(
           DateTime(1999, 2, 1, 12, 3, 42)) == -1);

assert(DateTime(1999, 3, 1, 5, 30, 0).diffMonths(
           DateTime(1999, 1, 1, 2, 4, 7)) == 2);

assert(DateTime(1999, 1, 1, 7, 2, 4).diffMonths(
           DateTime(1999, 3, 31, 0, 30, 58)) == -2);

Authors

Jonathan M Davis

License

Boost License 1.0.