when subtracting two dates we need to be careful not to produce negative durations when that doesn't make sense
when subtracting two dates we need to be careful not to produce negative durations when that doesn't make sense

1nickt/DateTime.pm,1nickt/DateTime.pm,autarch/DateTime.pm,autarch/DateTime.pm,1nickt/DateTime.pm,chansen/DateTime.pm,chansen/DateTime.pm,chansen/DateTime.pm