This is a question about calculating elapsed time using two fields
of type time, when the later once is past midnight.

I've recently converted tables from Paradox, where I used datetime
data types. In the firebird tables, I used date and time datatypes,
thinking there might be some advantage.

I want to write a stored procedure that calculates the elapsed time.
I have what amounts to start_time and end_time fields. It seems that
I need to subtract the milliseconds of the start_time field from the
milliseconds in a day, and then add to the result the milliseconds
of the end time, then convert to hours (floating point).

But I don't know how to do that. I've tried variations on cast() but
can't get them to work.

Using Firebird 1.0.3.

Steve