Disney Channel announced that the project had started production in November 2020; filming was expected to continue until mid-December (via The DisInsider). It was shot on location in Chicago, Ill., according to the Chicago Sun-Times. As a holiday movie, "Christmas Again" has certain deadlines it must meet to capture its seasonal audience, so the fact that it's coming after Thanksgiving and before Christmas is no surprise.
On Aug. 18, Disney Branded Television announced that "Christmas Again" would debut on the Disney Channel at 8 p.m. ET on Friday, Dec. 3 (via Disney Plus Informer).
Once it's shown there, the TV movie is expected to move to the Disney+ streaming service, but there's no word yet on when that might happen. So, if you want to catch it as soon as it's out, you might need to set your DVR. However, Disney often airs its movies multiple times, especially if it does well in the ratings, so you might be able to catch it a few times during the first month of winter.