Adjective to describe that a date is now in the past

Question

I'm trying to formulate to a website user that he can't modify a date anymore because this date is now in the past.

So for I'm at "You can't modify a campaign start date after it's exceeded" (campaign here means advertising campaign, if that's of importance), but I have a gut feel that "exceeded" is incorrect, and that the sentence is overall weak.

Is there a better adjective ? Should I fully reformulate ?

Answer 1

There are many ways to express that idea. Here's one:

A campaign's start-date cannot be changed after the campaign has started.

P.S. Another way is to use once:

Once a campaign has started, its start-date cannot be changed.