I looks like that your Database doesn't recognise the string as a date. Check what it does accept and format your date accordingly. If you don't have any documentation select back a date and look at how it is formatted. It will most probably accept that as an input
For easy date formatting I often use the POSIX module's strftime routine to format the date. e.g.
use POSIX qw(strftime);
my $cur_time = strftime "%m %d %Y", localtime;