VSTS Wiki Preview Incorrect

I'm editing a Wiki page and I started to enter a date in YYYY.MM.DD format and the preview is wrong. Am I doing something wrong?

In the edit page I've got '2017.' but in the preview it reads '17.'.

Solution

It seems the Wiki page treat 2017. as a number list. I posted a problem Format YYYY. in VSTS Wiki page doesn't show correct, you can follow up.

But the format for YYYY.MM.DD is correct. You can continue entering MM.DD (such as 09.26) following 2017. (without blank space), the preview will be as expected 2017.09.26.