How to combine date and time values into a datetime value

[RedVox]

I have a three columns: [datetime], [date] and [time].  I want to populate [datetime] using values inputted by the user in the [date] and [time] columns.  I thought this would work:

= DateTime([date], [time])

but it does not.  Any help much appreciated!

Why am I doing this: My app shares data with a web app that presents calendars using a datetime value rather than seperate ones as Appsheet seems to do.  

[RedVox · Accepted solution]

I figured it out.  The answer is [Date] + ([Time] - "00:00:00"), which seems like the most unintuitive of possible answers!