Achievements on offline mode

Some games will, others won't.

Im not sure.

I didnt think so as ive missed several when my connection wasnt working but in other games they seem to work.

OK, thanks!

for a data point:
was playing Unmechanical the other day when my internet went out, unbeknownst to me. got a bunch of achievements, but the timestamp for them all was when I logged back in to steam. so yeah, your timestamps might suffer.

I've read a thread once where someone said that you have to run the game at least once online for some reason, then after that, you start getting achievements when playing offline mode for the game.

It depends on the game. My advice would be to just try to get an achievement offline with the game in question. Worst case scenario: you have to get the achievement again online.

yeah, in some games, my borderlands is all goofy

Yep. Got all of my Skyrim ones in offline mode. Two playthroughs, when I checked, 0 hours played. I had no internet connection at the time and I don't even remember having Steam on when that happened, but apparently I did. Trying to get those 150 hours back, gradually.

Speaking of which...

All three outcomes have happened to me.

Played Bastion offline, did a couple who-knows-where runs, finished the game. When I logged in again, Steam didn't note either my hours or my achievements.

With Tropico 4, you had to log in to play - however, during play my connection died. Kept playing and finished a couple missions. Next day when I logged in again, all the achievements came popping up.

With Puzzle Agent 2, achievements keep kicking in during play even while I was offline.

On Payday the Heist I didn't have internet for a few days so I just stealthed diamond heist on overkill since I didn't need a team for that. I got the challenge, but didn't get the achievement until I next started it up online.

When I completed HL2 (Because I had no Internet) - All the Achievements I got never got added once I connected back to the steam server, kind of a disappointment.

The time played should also get updated, too :(