In Excel time if time is mentioned in hh:mm format (12:40 AM). Here if you need to add minutes to this time, a simple formula can be used.
Add minutes to time
Simply divide the minutes by 1440 and add to time in hh:mm format.
Another way is to convert minutes to format hh:mm by using formula TIME(hours, minutes, seconds)
Refer image above
Click here to download sample excel file
This guide applies Excel 2010 you can test on other excel versions Add minutes to time