The Batch Interface to restore database

I’m using Tamino v3.1.1.7 on AIX 4.3.3.
I have made a backup of the database to tape(backup medium:Tape).
One tape was made a backup at 08-AUG-2003. Other tape was made a backup at 26-AUG-2003.

I put a tape of 26-AUG-2003 on the tape device.
I used the following batch interface.
> argbatch restore database product=Tamino target=host user=tamino password=tamino database=testdb backupdate=08-AUG-2003:17:00:00 recoveryoption="no"

Tape’s date differ from a parameter value of backupdate.
In spite of difference, database finished the restore successfully.
Please let me explain the reason.
Thank you in advance.