When is a tag on a question counted for badges?

Question

The SE system tracks a tally of how many questions you answered for a given tag, and at certain thresholds, awards badges (bronze, silver, gold) for that tag, that at least for gold status come with additional privileges, like being able to re-open a question single-handedly.

But tags for questions can change over time: new tags can be added, old tags can be removed.

Does this affect the count, updating your status for the tag along with the question? Or does the system count the tags that were present at the time you answered the question, and does not update this later?

Answer 1

Your tag score is recalculated each day.

Quoting from this meta.se post:

What is a tag score?

A tag score is basically the combined total of all the upvotes (+1) and downvotes (-1) you've accumulated on answers under that specific tag (votes on questions do not count). Multiple answers to the same question will all count toward the tag score and number of answers. Community wiki answers and deleted answers do not count towards your tag score. Tag scores are only recalculated once daily, at 03:00 UTC.

So your score at the time of recalculation is a snapshot of the tag state of every question you’ve answered at that time. If tags change, it is reflected in your tag score at the time of the next recalc, and badge awards or revokes are executed whenever those scripts run.