General :: How To Set System Time In 12/24 Hr

When I use the `date' command on RHEL5, I can get the time shown in 24 hr format. I wonder if the time can be shown in 12 hr format. But I don't want to use the `date +FORMAT' to do that, neither `alias date='date +FORMAT''. I just want a simple `date' to show time in 12hr format.Is there any configuration file about the 12/24 hr format? Is the format related to the value of the environment variable 'TIMEFORMAT'? I can't find its default value by 'set | grep -i timeformat'.How can I know what the current format is? I mean, when I use `date', I can get "Sun Sep 19 13:22:50 CST 2010", which seems like 24hr format; but when I use `hwclock', I can get "Sun 19 Sep 2010 01:23:05 PM CST -0.174299 seconds", which seems like 12hr format.