That large number is epoch time, which equates to:
GMT: Sun, 01 May 2016 13:39:00 GMT
Your time zone: Sun May 1 08:39:00 2016 GMT-5:00 DST
It is the number of seconds that have elapsed since January 1, 1970 (midnight UTC/GMT).
As for the firmware, when you download, it is what Bobjazz said...