WSA stores ExpirationDate, LastDeepScan, LastScan, etc in UNIX time in decimal base.
To convert the time, find the registry key, select Decimal base
and paste it in this website
http://www.onlineconversion.com/unix_time.htm
Because the time is stored in a flat, incrementing format this means it's very easy to use in scripts.
You can use a simple IF math command to verify that scans have been run or anything else you want.
http://ss64.com/nt/if.html
I will be producing more of these posts as time goes on. Unfortunately Webroot doesn't document non-GUI aspects of WSA operation so I'm going to do it.