That's a good question. They all seem to have the same design elements. They all seem to have been minted in Athens. Perhaps researchers have figured out more specific dates, based on minor design variations (Athena smiling or not, the style of the A-theta-E, the style of other design elements, flan size, etc), and based on archaeological evidence. I don't know. I'm not an expert, in the area of Athena/Owl tetradrachms. I Googled the following : Athena owl tetradrachm variations I only looked at the first page of Google results. I found one interesting article, which seems to have some relevant information, regarding your question. The author calls these "classical" owls "mass owls" : http://rg.ancients.info/owls/ I haven't read the entire article thoroughly, but I found some interesting items. In the article, the author says the following : "Despite the popularity of Mass Owls, their dating and attribution is one of the great underexplored areas of ancient numismatic scholarship. Chester Starr in 1970 called this area a "wasteland" and said a die study of these coins, because of their sheer numbers, would be a "terrific labour." Peter van Alfen in 2009 described Mass Owls as "notoriously untrainable issues." Because of the number of dies used, David Sear told me in a 2009 email interview that he hasn't found a single die match over the years involving any of the Owls sent to him to authenticate..." However, the author seems to attempt to analyze the variations. He says the following : "Mass Owls that were likely issued earlier, compared with those issued later, tend to have the following characteristics: Athena has a wider, smiling mouth that can appear as a smirk rather than a short mouth that's neutral in affect or that curves slightly downward, forming a frown. Athena has a more protruding rather than a flatter face. The eye of Athena is smaller and more symmetrical, with the curve forming the upper half mirroring the curve forming the lower half, rather than the two sides being asymmetrical. The floral scroll on Athena's helmet is smaller rather than larger. The owl has shorter rather than longer claws. The ethnic consists of smaller rather than larger letters. The incuse square is more clearly visible on the coin's flan rather than being off it." He also says a bunch of other stuff, which I haven't read thoroughly. Maybe I'll read it later. So this article may be helpful. Also, there may be other helpful articles, on the other pages of Google results, or from other Google searches.
As with any ancient coin, I think we need to be comfortable with a degree of ambiguity, particularly when it comes for dating. To within 50 years isn’t bad considering we are nearly 2500 years removed from their montage. Luckily there is a recent book on the coins of Athens which I would highly recommend