It used to be that, when entering the month and date in a date field, without entering the year, calc would interpret the input as a date in the current year.
In 3.6 RC1:
* If I enter a date as 31/12, the year is not filled in, and the field is displayed left-adjusted, which means that it is not interpreted as a date. This is quite inconvenient, if a lot of dates have to be entered.
* If I enter a date as 31 Dec, the current year is appended automatically, and the field is displayed right-adjusted, with the date displayed in whatever format I have chosen.
*** This bug has been marked as a duplicate of bug 52240 ***
What locale are you working in?