Whats the best way to represent date and time fields with spec?


Hi everyone, I have a question and I would like to know if anyone here can help me.
What is the best way to via spec using date and time fields.

I’m using this way:
(s/def :model.shift/initial-date #(instance? goog.date.UtcDateTime %))
(s/def :model.shift/start-time #(instance? goog.date.DateTime %))
(s/def :model.shift/end-time #(instance? goog.date.DateTime %))

And how could I use exercise with this fields?