A few days ago we passed the 1,500,000,000 seconds universal time mark. Unix epoch time rolled over to 1500000000:

$ date -d@1500000000 -u
Fri Jul 14 02:40:00 UTC 2017

You'll find this number of seconds as "ModTime" in the API results, looking like this:

           "ModTime": 1500000911,
           "WorkunitId": 146184369,
           "ResultId": 1618031161,
           "Name": "FAHV_1003359_3j3q-k9-P3_32198_0",
           "Outcome": 1,
           "ReceivedTime": "2017-07-14T02:55:07",
           "ReportDeadline": "2017-07-23T13:58:33",
           "SentTime": "2017-07-13T13:58:33",

Unix timestamp 1,500,000,000 seconds at TimeAndDate.com
(Unix time (also: POSIX time or epoch time) is the number of seconds that have elapsed since 1 January 1970 00:00:00.)