When I click the next and previous arrow buttons or swipe left or right on the ion-datetime component it skips every other month. This behavior can be replicated on the documentation page ion-datetime: Ionic API Input for Datetime Format Picker
There are a few issues open for months flickering or having issues and I believe the next update is coming to resolve it. Here is what I found: https://github.com/ionic-team/ionic-framework/issues?q=is%3Aissue+is%3Aopen+datetime+month
[Edit] Sorry your issue might be new and might be worth opening up a new issue actually.
I too see the months skip on the demo, nice catch! ion-datetime: Ionic API Input for Datetime Format Picker
Thanks, I just submitted a new issue for this behavior.