I have done this before using Automations to help capture the value when a record is added. To set it up you create a Time of Day field (In this example called Time) and a formula Time of Day field (That I named Time of Day) that is set up using the formula:
ToTimeOfDay(Now())
It strips out just the time component of Now() and has it set up in a field to be captured. Then I created an Automation on my table so that whenever a record is added to this table it will capture the value in the formula Time of Day field and copy it into the manual entry field. I also just add a filter so that the only record edited is the record with the exact same Record ID# as the one that triggered the change. This example just captures the Time a field was created but the Automation itself could be edited to only trigger under certain conditions, for example capture the time when a specific field was edited or even when a specific value was selected using the Automation features. The set up for the basic Automation looks like the image below.
I hope this is helpful in pointing you in the right direction.