I am assuming when you are comparing greater than or less than you mean epochNumber of _time is greater/less than epoch number of "2016-01-01". Give this a try please and adjust greater than or less than according to your like in eval status1 command:
yourBaseSearch to get the _time
|eval myNewTime=strptime("2016-01-01", "%Y-%m-%d")
| eval time1=strftime(_time, "%Y-%m-%d")
| eval epoch_time=strptime( time1, "%Y-%m-%d")
| eval status1=case( epoch_time < myNewTime, "Yes", 1=1, "No" )
| table _time, epoch_time, myNewTime, status1, Name, Rank
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