I did a write-up for someone on this not too long ago.
CWM Naming convention:
YYYY-MM-DD.HH.MM.SS
You can rename them to whatever you want pretty much. Just stick to numbers/letters/-/. and you should be fine. Other special chars may work... but meh. I *know* spaces will cause you to get an MD5 checksum error. Removing the space will make it work again, I'm guessing that when CWM runs it's checksum it doesnt wrap the filename in quotes, so it basically cant find the file with anything after the first space. Hopefully that made sense.
Personally, I like to rename the backup while in CWM. Usually I do my backup ,then flash a new rom anyway. While the new rom is flashing, I just:
adb shell
cd /sdcard/clockworkmod/backup
(find the new backup)
mv new-backup-filename whatever-you-want-to-call-it
Now. The reason that your backup names don't make sense by default is that his phone doesn't have a true hardware clock. Therefore when you're in recovery it defaults to 1970. You can see the same thing happen if you turn your phone off for a bit and turn it back on in an area without service/internet.
Hopefully some of that helps.
*edit*
I found
this... It may or may not work. I'll mess with it later on and see how it plays out. Worth a look though.