Unable to read input values from ion-datetime when displayFormat="mm'ss""


I wrote a simple interface to get a time value as input from the user.
The time has the following format: mm’ss" so I want the user to put a time value in minutes and seconds, using such ion-datetime picker so that she can’t put wrong values in.

Here’s the small piece of code I inserted:

<ion-datetime placeholder="in mm'ss&quot;; es. 01'04&quot;" style="text-align: right;" displayFormat="mm'ss&quot;"

Unfortunately, after selecting the time, the time variable is not getting updated. It’s like it doesn’t like such date-time format. Actually, I tried to change it to a real date (namely, changing format to displayFormat=“MM/DD/YYYY”) and the time value correctly gets the date via ngModel.

Why is this not working when dealing with minutes and seconds?