Hi,
The time format is known as Unix time and is in the Epoch format:
http://en.wikipedia.org/wiki/Unix_time
For Excel you can use the formula:
/ 86400 + DateValue("1/1/1970")
Also remember that the time is based on whatever time format you installed the CUCM in so if it was GMT but the calls you are actaully looking for at GMT +1 you need to add 1 hours:
/ 86400 + DateValue("1/1/1970") +3600
,Best regards
Mackers