Time formulas:make a schedule for printing

[famdamly]

I went to make a schedule for printing out for manual fill in.
I changed the format of column A to time.
I entered the first time in A3

A3 6:00am
A4 =A3+:30 didnt work
A4= A3+30 didn't work
A4=A3+.5 didn't work
Those were just guesses.
What's the right way?

[Dave O]

In A4 the formula is
=A3+(30/1440)
.... where 1440 = 60 minutes x 24 hours. To Excel, a time such as 6:30
am is the fraction of a day. Each day is an integer number; a time
during that day is the integer number plus a fraction.