December 22, delays are always possible but it's not going to launch earlier than that ("no earlier than" is often abbreviated "NET" in that context).

https://jwst.nasa.gov/content/webbLaunch/countdown.html

Well. It has shifted to the 24th now: https://blogs.nasa.gov/webb/2021/12/14/webb-space-telescope-...

As an extra question: when do we start getting data? Specifically, how long until we can start finding out if planets around other stars have oxygen, or even industrial pollutants like CFCs (my understanding is that if we see CFCs, it's almost certainly due to complex life and couldn't be a natural phenomenon. Oxygen is unfortunately more ambiguous, apparently).

Ever since I heard about JWST (I feel like it's been 8 years ago now), I was looking forward for an answer to this question. All the delays have been so painful...

First light (or do IR 'scopes do "first heat"?) in June, 2022, if all goes well:

https://www.nature.com/articles/d41586-021-03620-1

30 days to achieve orbit.

Six months to settle, synchronise, allign, and calibrate.

December 22nd; they were aiming for the 18th but there was a small issue that required a bit of additional testing so they pushed it back to the 22nd.

Wasn't the most recent 18 -> 22 delay because they dropped it?

They didn't drop it but a clamp released unexpectedly during some operation and it caused vibrations in the telescope. At that time they didn't have sensors attached that would be able to confirm if the vibration was within specified tolerances so manual inspection of sensitive components had to be done again.

Glad to hear it went well and we are back on track!

Yep.