In entry #292, you may recall seeing these two expressions:
Merci pour tantôt.
Désolé pour tantôt.
In both cases, tantôt refers to a moment in the recent past. In other words: thanks for earlier on; sorry for earlier on.
Another example of tantôt:
Il nous observe depuis tantôt.
He’s been looking at us for a while.
You’re in luck — you can hear this sentence in the clip Rencontre du deuxième type, which has been providing lots of good material in the past few entries!
If you want to listen, you can hear it at 0:44 in entry #376, #377 or #379.
Tantôt can also refer to a moment in the near future. For example, you’ll often hear the following expression when people are saying good-bye to each other for the moment:
À tantôt!
It means something like “see you in a bit” or “see you shortly.” It’s equivalent to à tout à l’heure or à plus tard. The next time you’re saying good-bye to a friend whom you’ll see again later on the same day, you can say à tantôt!
By the way, the expression à tantôt is also used in Belgium in this same sense, so I guess we can’t say that it’s québécois! Maybe we’ll have to call it an expression belgiquébécoise...