Total time counter (C#)

I would like to add a variable that contains the Total Time spent in game (if possible in Int format). But i want the timer to be counting only for the lifespan of a specific object. And when the player checks his stats,make it so he can see the time in HH:MM format (no seconds).

Thanks in advance!

EDIT: Would a fixed update help me ? If yes,can i change the counter to go up every (N) seconds ?

Use PlayerPrefs.SetInt() and Time.realtimeSinceStartup.

The time format will have to use your awesome (I know you have them) maths skills to work out the hours and minutes from a number in seconds.