# Check if date time input is valid. If valid return 1, else return 0
# Adapted and expanded to cover time from:
# http://www.regular-expressions.info/dates.html
sub valid_date_time
{
my $input = shift;

if ($input =~ m!^((?:19|20)\d\d)[- /.](0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01]) \s+([01][0-9]|2[0-3])[/:.]([0-5][0-9])[/:.]([0-5][0-9]) $!)
{
# At this point, $1 holds the year, $2 the month and $3 the day,
# $4 the hours, $5 the minutes and $6 the seconds of the date/time entered
if ($3 == 31 and ($2 == 4 or $2 == 6 or $2 == 9 or $2 == 11))
{
return 0; # 31st of a month with 30 days
} elsif ($3 >= 30 and $2 == 2)
{
return 0; # February 30th or 31st
} elsif ($2 == 2 and $3 == 29 and not ($1 % 4 == 0 and ($1 % 100 != 0 or $1 % 400 == 0)))
{
return 0; # February 29th outside a leap year
} else
{
return 1; # Valid date/time
}
} else
{
return 0; # No valid date/time
}
}