date comparision

I am wriitng a shell script to compare a date in `date +%Y%m%d%H%M` to the output of `cat /var/adm/messages.0 | grep Temp |grep "CPU Fans" | cut -f1-4,19 -d' '` which looks like

Dec 2 11:30:57 79
Dec 2 11:37:58 79
Dec 2 11:44:58 79
Dec 2 11:50:59 79
Dec 2 11:58:00 79
Dec 2 12:05:01 79
Dec 2 12:11:01 79
Dec 2 12:18:02 79
Dec 2 12:21:02 80

How can I do this . My main issue is abbreviated month description .

Many thanks in advance

a=2007-05-10 (YYYY-DD-MM Format)
b=2007-06-10

These are the two given dates and I need to compare.
(First It should split the dates into YYYY,dd,mm)

The script should first compare years(2007 here).If both are same or if "a" is lesser than "b"(ie.suppose year in "a" is 2006),it should print correct.If "a"(ie. suppose year in a is 2008) is greater than b,then it should print error.Similarly for the dates(05 and 06).

No need to check for the months(10).

Regards,
Dave Nithis.