Well, for HOTS and WOL, you add up all the time in the missions, then you multiplied it by 0.725 to get the accurate in-game time (since time was sped up in those two versions). However, I don't think you have to do that with LOTV since it's in game time goes at the same rate as normal time. So, you'd just add up all the time during the missions (including things like restarts), and then that would be your in-game time.

Can in-game time be added to LOTV? It's on both WoL and HOTS, shouldn't it be here too?