Since hay is for horses , you should never spell this word hayday. By remembering this tool, you can always remind yourself that heyday is the correct version of this word.

I will outline which of these two spellings is correct and the correct context in which to use it. Although heydey saw a brief period of infrequent use during the first half of the 20th century, very few writers have ever used the hayday spelling.

I will also give you a mnemonic device that you can use when choosing either heyday or hayday becomes difficult. This trend holds true in both American and British English, as you can see in the charts below.