Er... No, I brain farted. The diphthong in "day" is /eɪ/. /aɪ/ (which I was listing as /ai/ on my phone) is as the word "tie".

So maybe that makes it more obvious why it would be easy to confuse /e/ and /eɪ/, especially when your native language only has the latter. Brain heuristics work regardless of whether you want them to or not, and they'll fill in the missing /ɪ/ even if it's not present.