A mini RMAN recovery quiz

A few months ago, I have come across of an interesting circumstances while doing an RMAN point-in-time-recovery (PITR)  on one of our business critical RAC databases. I thought it would be worthy to blog about the interesting scenario that I come across. Ok, I need to take my memories back in time to explain what had happen.
At that time, I was advised to rollback the database using the last night ONLINE RMAN backup and recovery (forward) it to a particular point in time. I was able to restore the database successfully using the last night backup.  However, while doing the recovery, RMAN was requesting archived logs that were generated almost a week back. I was surprised a little bit about this behavior as I was in a impression that RMAN looks for the archived logs that were generated after the online backup. Though I have restore and recover the database successfully to a PIT, I thought of conducting a mini quiz on this behavior to get cross your perspective on this, before I reveal the secrets  and blog about it. So, here goes your quiz:

    Under which circumstances does an RMAN recovery needs archive logs generated before the backup sets that are used in the restore operation?

Best of luck and awaits for your response....