Date formatting Unity 5.4+ vs 5.3

I have a project where I display a date (dd/MM/yyyy) and, when I load the project in Unity 5.4+ the formatting fails, whereas in Unity 5.3.3f1 it works fine (see image below).

82663-untitled-1.png

Nothing has changed in the code, can anyone point out what gives? I’ve tried googling, but couldn’t find any leads on to what might be causing the problem.

This is how I format it:

dateTimeInputField.text = dateTime.ToString( @"dd/MM/yyyy" );

Hi @Dam-Pete, i used this code:

Debug.Log(System.DateTime.Now.ToString(@"dd/MM/yyyy"));

in Start() function on unity versions 5.3.2f1, 5,4,2f2, 5.5.0b10 and always get the same result:
22/11/2016.