There is no specific date or month for that. But traditionally retailers begin advertising for Christmas after Thanksgiving Day, which is 22nd of November.
Although both holidays have become very commercialized, I believe Christmas is more commercial. Mostly because retailers begin advertising Christmas earlier every year and target gift giving.
1750
1987
Christmas is on the 25th of December
uhm, to celebrate christmas
see link "Christmas"
Advertising makes Christmas a more commercial holiday. There is more about buying toys and gifts than about celebrating love, family, and religion, rather than the religious holiday that it originally was. It's no longer as much about the birth of Christ as it once was. Nowadays, people try to sue if there is a nativity scene put up in the city, which also shows how skewed the perspective has become. ( since without that scene there wouldn't be a Christmas to begin with...).
In the early 1900s, Florsheim began advertising nationally in magazines such as The Saturday Evening Post
Becuase Christmas is freaking awesome!
The story A Christmas Carol begins on Christmas Eve.
after realizing that advertisement is not going to be famous.
If it's new, the answer is to start advertising immediately. Advertising will help build your reputation and build a clientèle. As soon as you exist you want to advertise.