History records having missing stimes

I am seeing history records that have stimes. I don’t understand why do some of these records of missing start times on history records.

For example

VID HOSTNAME        ACTION           REAS     START_TIME       END_TIME MEMORY CPU  NETRX  NETTX   DISK
1580 Cloud-csmall-SP poweroff-hard    user              - 05/19 13:35:16   9.8G   1     0K     0K   4.9G
1580 Cloud-csmall-SP poweroff-hard    user              - 05/19 16:34:02   9.8G   1     0K     0K   4.9G
1580 Cloud-csmall-SP none             user              - 05/19 16:40:18   9.8G   1     0K     0K   4.9G
1580 Cloud-csmall-SP terminate        user              - 08/16 18:15:31   9.8G   1     0K     0K   4.9G

Not sure on how to reproduce this. This is happening to some vms we are managing through opennebula