Detect daylight saving time in bash

Question

I want to detect if I'm in winter or summer time. My current approach is:

if date +%Z | grep -e CET -e EST; then
  # I'm in winter time
else
  # I'm in summer time
fi

which have obvious drawback as you have to know all the timezone names.

Answer 1

Perl to the rescue:

if perl -e 'exit ((localtime)[8])' ; then
    echo winter
else
    echo summer
fi

That's because localtime returns the following list:

#     0    1    2     3     4    5     6     7     8
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
                                            localtime(time);

where "isdst" stands for is daylight saving time.