Forget MM/DD/YYYY vs DD/MM/YYYY debates! Some evil frontend developer decided the best date format is "YYYY/DM/DM" and expects users to calculate their own birthday. It's like telling someone "your birthday is in 1990, now solve for x where x equals the day you were born divided by the month, twice." This is what happens when you let the same person who named variables like temp1 , temp2 , and finalTempIPromise design your forms.