How to get the time that elapsed during a sleep (or a stop) when we are woken up by a pin wakeup ?

Hello,

I am using an STM32F4.

I need my mcu to go to sleep (preferably a stop) and i want it to be able to wake up because of a pin or a set timer.

My problem is that i am not able to know how much time has elapsed when i wake up because of a pin.

Does anyone have an idea of how i can do that ?