Where are the snapshots generated by schedules?

[WXR]

If I create a snapshot of a volume , I can see it on the snapshot list.
But if I create a hourly schedule for a volume and wait enough time(longer than 
1 day),I can't see any snapshot associated with the volume on the snapshot 
list.All snapshots listed are "manual".
I don't know if the schedule doesn't work correctly,or the snapshots are 
generated by schedule but not shown on snapshot list.