37 chars.

However, I would say two things about this. First using ' istead of :: is so ugly that it isn't worth the 1 stroke saving. Secondly, although Perl Golf involves bending the rules as much as possible, using modules just goes against the spirit of the game.

# 39
sub xmas1 {
    use Date'Manip;Date_DayOfWeek+12,25,pop
}

# 41
sub xmas2 {
    use Date'Calc':all';Day_of_Week+pop,12,25
}
[download]

Update: I saved 2 chars by using May Day instead of Christmas. The politics of that may appeal to someone. :-)

# 37
sub xmas3 {
    use Date'Manip;Date_DayOfWeek+5,1,pop
}

# 39
sub xmas4 {
    use Date'Calc':all';Day_of_Week+pop,5,1
}
[download]

--
John.