if `value == '12345765' # epoch time in a string` then `Time.parse` will explode and be rescued by `nil`, setting `result = nil`.  Then `value.to > 0` will be true && `result` will be nil (making the line you pointed to true).

All this boils down to:
1. If value is a string containing a parseable date, it will be parsed successfully
2. If value is a string containing epoch time, it will be `to_i`'d and subsequently `Time.at`'d