Date::Math::Add;
Date::Math::Subtract;
Date::Math::DaylightSavingsTime;
Date::Math::WeekdayCalculations;
Date::Math::JulianCalendar;
Date::Math::GregorianCalendar;
#etc etc.

##</code><code>##

my $math = Date::Math->new();

print $math->addition("2016/05/16", 5, "days");

if($math->daylightsavingstime_in_effect) {
    print "DST is in effect.";
}

print "That falls on a ", $math->weekday_name($math->addition("2016/05/16", 5, "days"));

##</code><code>##


my $mathadd = Date::Math::Add->new();
my $mathdst = Date::Math::DaylightSavingsTime->new();
my $mathweekday = Date::Math::WeekdayCalculations->new();

print $mathadd->addition("2016/05/16", 5, "days");

if($mathdst->daylightsavingstime_in_effect) {
    print "DST is in effect.";
}

print "That falls on a ", $mathweekday->weekday_name($mathadd->addition("2016/05/16", 5, "days"));