Last week we had a customer ask us which was correct, expiry date or expiration date. As a Canadian, both terms are familiar to me, so I decided to do some digging into these two phrases. Which is best to use? 
American Vs. British:
As with many expressions and words in English, it depends on where you live. American English and British English have some differences, and this phrase is no exception. When referring to the date when a product or service expires (such as milk or a passport), the British say expiry date and Americans say expiration date. Canadians often end up using both terms equally, but I’d be interested in hearing if there are differences depending on where in Canada you live (I’m in Vancouver, BC, and I hear both).
What’s more common online?
Googlefight checks which word or phrase gets the biggest number of results on Google. In this case, Googlefight shows far more results for expiration date (11,800,000) than expiry date (6,260,000). (Googlefight is stuck on French for me right now, but the results are for the English keywords.)
What’s more common in print?
A search via Google Ngram Viewer shows that expiration date has been used a lot more often than expiry date since the early 1900s.
Based on all of this, I’d say that it’s best to use expiry date in countries where British English is spoken and expiration date in North America. Of course, you could always use the terms best before or use by instead!
