You can add (or subtract) a number of minutes from a time using fractions.
Dates are represented as sequential whole numbers so 1 hour is equivalent to the fraction (1/24).
Times are represented as fractions based on there being 24 hours in a day.
1 Hour is 1/24 = 0.04166
1 Minute is 1/(24*60) = 1/1440
1 Second is 1/(24*60*60) = 1/86400

Example

 A 1 =TODAY() = Monday 01 July 2024 2 =NOW() = Monday 01 July 2024 06:51:44 3 =A2 + (25*(1/1440)) = Monday, 01 July, 2024 07:16 AM 4 =A2 + TIME(0, 25, 0) = Monday, 01 July, 2024 07:16 AM 5 =A2 + (4/24) + (75/1440) = Monday, 01 July, 2024 12:06 PM 6 =A2 + TIME(4, 75, 0) = Monday, 01 July, 2024 12:06 PM 7 =A2 + (6/24) + (30/1440) , (80/86400) = Monday, 01 July, 2024 01:23 PM 8 =A2 + TIME(6, 30, 80) = Monday, 01 July, 2024 01:23 PM

1 - Displays the current date. Custom format "dddd dd mmmm yyyy".
2 - Displays the current date and time. Custom format "dddd dd mmmm yyyy hh:mm:ss".
3 - Displays the current time plus 25 minutes.
4 - Displays the current time plus 25 minutes seconds using the TIME function to return the correct decimal.
5 - Displays the current time plus 4 hours and 75 minutes.
6 - Displays the current time plus 4 hours and 75 minutes using the TIME function to return the correct decimal.
7 - Displays the current time plus 6 hours, 30 minutes and 80 seconds.
8 - Displays the current time plus 6 hours, 30 minutes and 80 seconds using the TIME function to return the correct decimal.
All these cells have been formatted with the custom number format "dddd, dd mmmm, yyyy hh:mm AM/PM".

Built-in Functions

NOW - The date serial number of the current system date and time.
TIME - The time as a decimal given an hour, minute, second.
TODAY - The date serial number representing today's date.