There is no way in Unix to get a files creation time. You can find a files modification time, mtime, (you have ctime - the time when a files status was changed - check out the find man page), and if you can guarantee the file has not been modified since it was created, you have your creation time.

Anyway, the -regex looks to be an overcomplication.

find / ! -name "*.log" -mtime 45 | xargs shred -fuvz

If this doesn't work, chances are the files would have been modified after creation.

EDIT; if running this as root, and some important system files were modified 45 days ago, you are staring into the eyes of doom with a command like that.

Do a
find / ! -name "*.log" -mtime 45 -print
to see the output before adding the "destructive" pipe through to xargs shred.

Cheers
ZB