std.datetime: converting AM/PM to 24 hour format

[Timothee Cour via Digitalmars-d]

Not that it's hard to do, but would be nice to have this in std.datetime,
just ran into some data that was using AM/PM.
eg:
if(AMPM == "PM" && hours<12) hours = hours+12;
if(AMPM == "AM" && hours==12) hours = hours-12;