DateTime does not currently support GPS Week calculations. The only package that I could find on CPAN which does support GPS Week is DateTime::Precise. (Which is not a "DateTime" object!)

#Copyright (c) 2011 Michael R. Davis License BSD
perl -e '
use DateTime;
use Time::HiRes;
use DateTime::Precise;
my $dt=DateTime::Precise->new;
printf "%s\n", $dt->asctime;
my ($weeks, $seconds, $days)=$dt->gps_week_seconds_day;
printf "Week: %s, Seconds: %s\n", $weeks, $seconds;
print DateTime->new(qw{year 1980 month 1 day 6 time_zone UTC})->add(we
+eks=>$weeks)->add(seconds=>$seconds), "\n";
'
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All of the Math is in DateTime::Precise::gps_week_seconds_day

There is no license on DateTime::Precise. But, since the pre-fork is licensed "The Artistic License 2.0" this code should be as well. See RT 32186.

sub gps_week_seconds_day {
  my $self          = shift;
  my $epoch_seconds = $self->gps_seconds_since_epoch;
  my $week          = int($epoch_seconds/Secs_per_week);
  my $seconds       = $epoch_seconds - $week*Secs_per_week;
  my $day           = int($seconds/Secs_per_day);
  ($week, $seconds, $day);
}
[download]