Timeline?

[D.A.R.K.]

Both games seem to happen at the same time, one thing is for sure The Sacrifice and The Passing happen pretty much at the same time, when the Left 4 Dead 2 survivors arrive at the bridge, Bill is dead for like 15 minutes max. We know that The Sacrifice is the last campaign from Left 4 Dead and that The Last Stand and Cold Stream are spin-offs, this means they don't fit the sequence of events. We also know that Left 4 Dead happens before Left 4 Dead 2, but The Sacrifice and The Passing happen at the same time, this means both campaigns before them are also happening at the same time or at least close.

This is my timeline:
No Mercy > Crash Course > Death Toll > Dead Air > Blood Harvest > The Sacrifice.
                            Dead Center > The Passing > Dark Carnival > Swamp Fever > Hard Rain > The Parish.

I believe Blood Harvest and Dead Center happened almost at the same time, probably Blood Harvest at night and Dead Center the next day morning. Then we have The Sacrifice and The Passing happening at the same time. The Left 4 Dead 2's survivors reach the Left 4 Dead's survivors in about 15 minutes after Bill's sacrifice, so we go to Blood Harvest.

At this point, we know the survivors from Left 4 Dead went to an island to spend the rest of their days eating fish and drinking coconut water, while the Left 4 Dead 2 survivors go to The Parish to be rescued by the military.

I'm probably completely wrong, what do you think?

[supersand]

The maps are listed in chronological order when you pick a map (based on series)

Bills is probably dead more like a few hours or even a day or two. L4D2 Survivors are probably still in Dead Center when The Sacrifice happens.

[JAiZ]

Originally posted by D.A.R.K.:

I believe Blood Harvest and Dead Center happened almost at the same time, probably Blood Harvest at night and Dead Center the next day morning. Then we have The Sacrifice and The Passing happening at the same time. The Left 4 Dead 2's survivors reach the Left 4 Dead's survivors in about 15 minutes after Bill's sacrifice, so we go to Blood Harvest.

That is impossible, considering Blood Harvest and The Sacrifice are confirmed to be a week apart, as outright stated in the comic.

There also has to be more than 24 hours (but less than 48 hours) between Dead Center and The Passing, due to Coach saying "You've been killing zombies for the better part of two days" to Ellis.
Combined with the fact that the L4D1 survivors are explicitly waiting for the lingering horde to disperse after The Sacrifice, it's much more likely that Dead Center takes place on the same day as The Sacrifice, with The Passing taking place on the day after.