There are two ways to spell whiskey: ending with a “y” or an “ey.” Knowing what spelling to use is primarily dependent upon the country where the spirit is produced. The Scottish, Japanese, and Canadians spell it whisky (no e). The Irish and the Americans spell it whiskey.
A simple trick to remember this is if the country has an “e” in its name, they spell it “whiskey.”
United States. American Whiskey.
Ireland. Irish Whiskey.
Japan. Japanese Whisky.
Scotland. Scotch Whisky.
Canada. Canadian Whisky.
To add to the confusion, there are also exceptions to the rule (Makers Mark Whisky for example). Also, in typical lets-make-no-sense-fashion, the U.S. federal regulatory definition of the spirit spells Whisky. So clearly there is not even a national understanding of what is correct. Either that and/or some Scotch drinking law makers had a good laugh passing the Bill.
There is little to be gained in proving you are a whiskey spelling bee champion at a bar. If one should encounter a pretentious spirits “expert” making a big deal of how to properly spell whiskey, tell them to pass the bottle and quit being an asshole!