Consistent, no. Depends on what kind of tin, what brand, when it was made, etc., etc. Exempli gratia, C&D and GL Pease tins are normally either ink-stamped or, more recently, stickered with a grocery-style gun that denotes the XX/XX/XX month, day, year of tinning; while Escudo tins have a series of numbers perpendicular to the bar code reading 'XXXXXXXXXX' where the first two digits are the year, the second two the month, the third two the day, and the rest are batch numbers; while others may only be dated through the changes in tin art, tax stamps or educated guesswork. If you have a particular tin you're interested in dating, post some pictures--I'm sure the forum would love to help with the sleuthing!
Also welcome to the forums, and post an introduction in the new members section!