Date default entry changed

[RobSmy]

My spreadsheet used to default to the correct year: when I entered Mar 18 (for example) the computer correctly interpreted this as March 18, 2009 and would display the date however I formatted it.

Now, when I enter Mar 18, the date goes in as March 1, 2018

I have no idea why the default interpretation of my entry changed. Any idea how to tell Excel to default to the current year if the year is not included in the entered data?

[contaminated]

Easy solution is to reinstallation...
I had similar problem.. so I had reinstalled my office...