When you have a dateTextBox with min and/or max constraints on it, you can get an out of range indicator while you’re typing a valid date. For example if you have a dateTextBox with a valid range of 3/21/2018 to 3/31/2018 and you type 3/25/20 you will get an out of range message. I would expect this to see that adding 18 would make this a valid value, and not show the indicator until the control lost focus.
I’ve created an example on Plunker (but I don’t appear to be able to include a link for it for some reason), that has the current dijit dateTextBox, and my attempt at updating the intermediate validation. Before I try to figure out how to submit a pull request I wanted to check if this is an issue and something that should be updated, or if the way it’s working now is how it should be working.