TFP for the win!

If day 1 is January 1st, day 181 is June 30th and day 365 is December 31st etc, which one of the following days is in a different month to the other ones?

The pattern seems to suggest that the days are numbered sequentially, but that is just an assumption.

Maybe the days are just assigned random numbers?

In any case, the provided information is insufficient to conclusively determine a correct answer.