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find date given day weekday and a range of months

by kimlid2810 (Acolyte)
on Aug 22, 2014 at 19:32 UTC ( #1098370=perlquestion: print w/replies, xml ) Need Help??
kimlid2810 has asked for the wisdom of the Perl Monks concerning the following question:

greetings monks i have a slightly bizarre problem and i would be grateful if someone can offer some advice. i have 3 data. the day of a month eg: 28, the corresponding weekday eg: Thu, the year eg: 2014 and a range of three months eg: Aug, Sep, Oct like this:
my $day = 28; my $weekday = 'Thu'; my $year = '2014'; my @months = ('Aug', 'Sep', 'Oct');
Is there anyway i can figure out the exact date? Any module that would take this data and return something like:
my $date = '2014-09-28';
Any algorithm known or any advice? Thank you :)

Replies are listed 'Best First'.
Re: find date given day weekday and a range of months
by kennethk (Abbot) on Aug 22, 2014 at 19:50 UTC
    Not directly, because it's an under-determined problem. Under ordinary circumstances, days in February and days in March that share an ordinal value also share a day of the week. That said, you could perform the necessary search using the DateTime module, like:
    use DateTime; for my $mon (8, 9, 10) { if (DateTime->new(year => 2014, month => 10, day => 28)->day_abbr( +) eq 'Thu') { print "Hit: $mon\n"; } }

    #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

Re: find date given day weekday and a range of months
by poj (Prior) on Aug 22, 2014 at 19:47 UTC
    #!perl use strict; use Time::Piece; my $day = 28; my $weekday = 'Thu'; my $year = '2014'; my @months = ('Aug', 'Sep', 'Oct'); for my $mth (@months){ my $t = Time::Piece->strptime("$day-$mth-$year","%d-%b-%Y"); print $t->ymd."\n" if $t->wdayname eq $weekday; }
Re: find date given day weekday and a range of months
by Anonymous Monk on Aug 22, 2014 at 23:32 UTC

    TIMTOWTDI! :-)

    my $day = 28; my $weekday = 'Thu'; my $year = '2014'; my @months = ('Aug', 'Sep', 'Oct'); my @mons = qw/ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec /; my %mons = map {$mons[$_]=>$_+1} 0..$#mons; @months = map {$mons{$_}} @months; # convert @months to numerical my @dow = qw/ Sun Mon Tue Wed Thu Fri Sat /; my %dow = map {$dow[$_]=>$_} 0..$#dow; $weekday = $dow{$weekday}; # convert $weekday to numerical use POSIX qw/mktime/; # core use Time::Piece (); # core since v5.10 use DateTime (); # CPAN use Date::Calc qw/Day_of_Week/; # CPAN use Date::Manip qw/Date_DayOfWeek/; # CPAN for my $mon (@months) { my $date = sprintf "%04d-%02d-%02d", $year, $mon, $day; print " mktime: $date\n" # 0 = Sunday if (localtime mktime(0,0,0,$day,$mon-1,$year-1900))[6] == $weekday; print "Time::Piece: $date\n" # 0 = Sunday if Time::Piece->strptime("$day-$mon-$year","%d-%m-%Y") ->day_of_week == $weekday; print " DateTime: $date\n" # 1 = Monday, 7 = Sunday if DateTime->new(year=>$year, month=>$mon, day=>$day) ->dow%7 == $weekday; print " Date::Calc: $date\n" # 1 = Monday, 7 = Sunday if Day_of_Week($year,$mon,$day)%7 == $weekday; print "Date::Manip: $date\n" # 1 = Monday, 7 = Sunday if Date_DayOfWeek($mon,$day,$year)%7 == $weekday; } __END__ # Output: mktime: 2014-08-28 Time::Piece: 2014-08-28 DateTime: 2014-08-28 Date::Calc: 2014-08-28 Date::Manip: 2014-08-28

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