Can you elaborate?

There are 22, not 21 episodes to start. enter link description hereenter link description here

Well, first of all, we have to follow NBC. Wikipedia shouldn't be used as a source. They often have episode lists that do not follow the original, official seasons. You might be right about the show having 22 seasons, but we need actual proof of when each season started and ended.

https://web.archive.org/web/20130107070222/http://www.nbc.com/the-tonight-show/episode-guide/season-21/618304/
https://web.archive.org/web/20131112062147/http://www.nbc.com/the-tonight-show/episode-guide/season-22/826627/

Considering how long ago, it’s hard to find on the actual network (they are never good about old shows). In those cases wikipedia is actually useful. IMDB was also provided as a link and that should have the information needed.

Many networks that existed in the past have changed ownership, sold rights, etc. Counting only on the original network would mean you never find a source.

IMDB has the same issue. They often don't follow the original, official seasons. And IMDb and Wikipedia often have data that is different.

Then you’ll need to figure it out with whatever rules you have. As consumers of TMBD we have a lot of frustration with some of the rules and restrictions this service has. Especially for older shows if you won’t use a source other than an original that doesn’t exist.

Well, if you expect me to do all the work you're gonna wait a long time!