I was looking into differences between IGT (in-game time) when comparing two separate runs at the same RTA time and noticed the IGT seemed to be off by much more than what can be explained with FPS differences. I narrowed it down to section which occurs during the mission Portrait of a Killer and figured it must be happening when the taxi warp occurs. Powdinet and I discussed this for a bit, and here's what he discovered in the code:

As you can see, it has nothing to do with that mission, it's just something that can happen when you taxi warp. Its effect is also pretty minor, or so I think. Given that no one has ever noticed this while doing a run, it's safe to say it's never going to be more than a 10-20 in-game minute increase. In the following pastebin, you can see its effect. Josh's PB, seen at the bottom, is a prime example. No more than 9 in-game minutes should have passed, but he ended up 30 minutes ahead.

http://pastebin.com/f3Q7K7iY

I did notice cabbing sometimes passing time and sometimes not passing time at all. I don't think it is random.

The simple reality is that this was Josh's first run and he was just too slow to complete the mission. He didnt set a marker instead searched for the target and between the moment when he gets out of the menu he loses massive time because of slow play.

Not because of cab times gone wild.

EDIT: Also further more the point where Joshimuz took the cab is very different from where you normally take it. Also the yellow marker.

You can't assume it has anything to do with a yellow marker, because it happened to others, many times, without it. Also, it isn't intended for time to pass when you warp with the cab. Start up your game and warp around over and over and I guarantee that you won't see the time change at all. If this were intended, it wouldn't fail 99% of the time.

You're clearly not understanding what happened in Josh's video. He exits the menu at 8:02 and he's in a cab and warping in under 15 seconds. The phone reads 8:32 when the warp finishes. 17 REAL seconds pass between these two points, and the in-game time advanced by 30. There's no denying the taxi warp progressed the time by ~20 minutes.

Edit: http://pastebin.com/8Gxc7Lb8

There are many points more to compare and I will most likely do so for now.

I also noticed when I compared a 9:36/9:38 First Date to your 9:25. Even though I frame limit in It's Your Call, there is barely a difference (maybe 0,1 seconds?). I should be saving 1.5 seconds over you, yet I don't.

Could someone change the title of this thread to "Taxi Warping In-Game Time Progressions"?

I recently came back to this issue and discovered the cause. These time progressions will occur every single time you use a taxi warp as long as something is scheduled in the phone's organizer and the map marker for the appointment hasn't appeared. Time progressions are relative to the distance the taxi needed to travel and are not variable for any other reason. During the Any%, Classic and 100% runs, there are two appointments which will show up in the organizer, the interview and the date with French Tom.

This paste shows the info I need for my current route - http://pastebin.com/frQmHF8z