The %DIFF function calculates the difference between two date, time, or timestamp values and returns the result in the specified unit. It can find the difference between dates, times, or timestamps, and supports units like days, months, years, seconds, minutes, and milliseconds. The first two parameters must be compatible date, time, or timestamp types, and the third parameter specifies the unit of the returned difference.

1.  %DIFF (Difference between Two Date, Time, or Timestamp Values)
The structure is as given below:
%DIFF(op1:op2:*MSECONDS|*SECONDS|*MINUTES|*HOURS|*DAYS|*MONTHS|*YEARS)
%DIFF(op1:op2:*MS|*S|*MN|*H|*D|*M|*Y)
%DIFF produces the difference (duration) between two date or time values. The first and second parameters must
have the same or compatible types.
The following combinations are valid for getting the difference:

Difference b/w two Dates

Difference b/w two Times

Difference b/w two Timestamps

Difference b/w Date and timestamp (only the date portion of the timestamp is taken to have the difference)

Difference b/w Time and timestamp (only the time portion of the timestamp is taken to have the difference)
The third parameter specifies the unit in which the difference will be. The following units are valid:

Difference b/w two dates or Difference b/w a date and a timestamp: *DAYS, *MONTHS, *YEARS

For two times or a time and a timestamp: *SECONDS, *MINUTES, *HOURS

Difference b/w two timestamps: *MSECONDS, *SECONDS, *MINUTES, *HOURS, *DAYS, *MONTHS,
*YEARS
Example
/FREE
num_days = %DIFF (date1: date2: *DAYS);// It returns the no. of days b/w date1 & date2
time = time + %DIFF (time1: time2: *minutes);// It returns the min. b/w time1 & time2
/END-FREE