Question though. Date input by typing is not usually a fast thing, so this option would not help in all cases. Would having an OnChange event that fires only when user leaves the input field be better in this case?
When you think about it, date input using the date picker icon and popup is only usefull if the date you wish to pick is located in the current month. But once you have to click on the month to pick another month and then on the date and, most of all, if you have to click on the year to change the year (scroll down/up to find it), then date input by typing is way much faster (another example is entering birthdates which are usually located far away from the actual date).
About the events, there is already an OnChange event on date fields. But, as it is recommended by MS articles on the best practice in PowerApps development, the goal is to detect any typing or data error as the user is typing. That's why, likewise for the text input controls, I would find more interesting to have DelayOutput on date fields because then, error message would show with some delay after the user stops entering the date.
Here is a user case I'd like to achieve properly with the DelayOutput property on date fields:
on a form I have 2 dates: BeginDate and EndDate
the user enters a BeginDate
once the user as entered a date for EndDate, after a short delay if the EndDate is located before the BeginDate, then I set the ErrorMessage text to: "EndDate cannot be prior to BeginDate"
Today I can achieve this by using the OnSelect event but then the error message shows up a bit too fast... That's what the DelayOutput is for right ? To show error messages with a delay of 500ms or so...
Adding @FilipK from the controls team.