What is a formula to calculate the difference between two date/time fields in hours:minute (both date/time values in 12-hour clock format)?
Finding the Elapsed Time Between Date/Times
To find the difference between two Date values, subtract one from the other like so: date_1 — date_2 to return the difference in days.
Finding the elapsed time between two Date/Time values is slightly more complex. For simplicity, the custom field Diff_c refers to the difference between two Date/Time values. Since Diff_c is a number, you can use this formula to convert it to days, hours, and minutes.
IF( Diff_c > 0 , TEXT( FLOOR( Diff_c ) ) & " days " & TEXT( FLOOR( MOD( Diff_c * 24, 24 ) ) ) & " hours " & TEXT( ROUND( MOD( Diff_c * 24 * 60, 60 ), 0 ) ) & " minutes", "" )