There are two kinds of date on a bag of coffee, and the one printed largest is usually the one that tells you least. Supermarket bags lead with a best-before date. Good roasters lead with a roast date. The difference is not a labelling convention. It is a statement about what the seller expects you to care about.
A best-before date tells you when the coffee stops being safe and saleable. A roast date tells you when it stopped being good. Coffee does not spoil in any way that will hurt you, so a best-before date on coffee is close to meaningless as a quality signal. When a roaster prints one two years out and no roast date at all, they are telling you they do not know when it was roasted, or they do and would rather you did not.
What is actually happening inside the bag
Roasting fills the bean with carbon dioxide. That gas escapes over the following days and weeks, and while it is escaping it does two useful things: it pushes oxygen away from the coffee's surface, and it produces the crema and the bloom that tell you the coffee is alive.
Once the gas is gone, oxygen gets to the oils. Those oils carry most of what you actually taste. Oxidised coffee oil is what produces the flat, cardboard, faintly rancid quality of old beans. Nothing about that is dangerous. It is simply no longer the drink you paid for.
This is why the useful window is measured in weeks. Most roasters and most of the reference literature converge on a similar shape: espresso wants a few days of rest and is at its best somewhere between about one and four weeks off roast, filter coffee is drinkable sooner and holds a little longer, and whole beans hold far better than ground. Ground coffee has vastly more surface area exposed to air, which is why a bag of pre-ground goes flat in days rather than weeks.
A two-year best-before date is compatible with all of that being long over.
The one-way valve is the other tell
Look for a small plastic disc on the side or base of the bag. That is a one-way degassing valve, and it lets carbon dioxide out without letting oxygen in.
A valve is a sign the roaster expects the coffee to still be off-gassing when it reaches you, which means they expect it to be fresh. A bag with no valve, sealed flat, is either very old, or was allowed to sit and degas in the open before packing. Neither is what you want. This is not a guarantee, because a valve costs almost nothing and can be fitted to a bag of anything. But its absence is informative.
What a roast date will not tell you
It will not tell you the coffee is good. A badly roasted coffee, roasted this morning, is a fresh bad coffee. Freshness is a floor, not a ceiling, and a lot of people buying their first bag from a specialty roaster expect the date to do more work than it can.
It also will not tell you how the coffee was stored between the roastery and you. A bag roasted ten days ago that spent nine of them in a hot shop window is in worse condition than one roasted three weeks ago and kept cool and dark. The date is a proxy for condition, not a measurement of it.
And it will not help you at all if you buy more coffee than you drink. A dated bag you open in week six is still a stale bag. The date is only useful in combination with buying an amount you will actually finish.
The honest recommendation
Buy bags that carry a roast date, buy an amount you will drink within about a month, and ignore the best-before entirely.
If a shop sells coffee with no roast date anywhere on the bag, that is not automatically bad coffee, and plenty of perfectly pleasant supermarket coffee is sold this way. It is simply coffee sold on a different promise, where consistency and price matter more than peak flavour. That is a legitimate thing to want. Just know which promise you are buying, because the two are priced as though they were the same.
We sell the objects the coffee goes into, not the coffee. So this is advice we have no commercial stake in, which is exactly why it is worth reading here rather than on a roaster's own page.