hmmm sounds an unusual problem there! all i can suggest it making a "genius appointment" at your local apple store, go and show them.
they only get allocated 15 mins per person and if they cant fix it there and then (which i doubt they will) then they will replace the handset.
just make sure you sync your iphone before you leave so it backs up all your data, when you plug in your new one (if you get one) itunes will prompt that there is a previous phone backed up and would you like to restore from the backup (yes!) or as a new phone (no!), then once the restore is complete your phone should look and act like it did before - minus the annoying clock issue! ;o)