I have two fields `dateTS` and `closingTime`.

* `dateTS` is a normal timestamp field (e.g. 2019-07-13 22:31:10.000000)
* `closingTime` is a HH:MM format of when a store closes (e.g. 23:00)

I need a PostgreSQL query to subtract the two field and get the number of minutes difference between them.

Using the examples given above the difference between the two fields would be 28 minutes

So far I've tried different variations of the datediff function, but it won't work.

My guess is I either have to

* a. generate a fake timestamp for `closingTime` which is the same day as the `dateTs` field and subtract the 2 timestamps.

or

* b. convert the hour/minutes of both field to a float and subtract the two values to get the hours difference and convert that to minutes