Hi,
Usually, people don't need to select a precise time of the day. For example, for delivery date selection, the day is usually all that's needed, and when time is also needed, it's usually a time range (for example from 9 am to 10 am, or from 10 am to 11 am).
And to do that, you can create a second custom field of the type "single date picker" and enter the different time ranges you want to be available to the user).
You could even have two fields, one for the hours and one for the minutes if that's really necessary.