Most of the time, the tin will not have a date marked anywhere on it, and that's where some detective work on your part is required.Dating tins isn't difficult to do, though it may involve some of your time.
You will be fortunate to date your tin right away, most of them will require you to carefully study their appearance both from a structure stand-point and how they are decorated or finished.
Some very obvious clues may not be sufficient, may be misleading, or have to be combined with other knowns to arrive at an accurate or close approximate date.
Let's start off with some general things that apply to most 20th century tins and to some 19th.
Addresses on tins can often be linked to a time period, even down to the exact year, if you use an old city directory or telephone book.
I live in Europe, and we don't have those marks on the packs.