The Academy Awards occur every late February and films that win awards typically see a boost in sales. To take advantage of this, the studios release films they deem "Oscar worthy" in the fall, before the eligibility cut-off, so that the films remain fresh in the memories of critics and Academy members right before the Awards, increasing their chances of being nominated. [Wiki]
If this is true, the chance of being nominated for an Oscar can be increased by releasing films later during the year or closer to eligibility cut-off. It appears from the graphic that most studios do this already. Below graphic has all Oscar nominations and winners for Best Picture in the last decade.
You may observe that most nominations and winners are clustered during 4 months (Oct, Nov, Dec, Jan) prior to Oscars and seems like the studios are strictly adhering to release of Oscar worthy films during these months. Also, November seems to be the most auspicious and lucky month since it has highest percent of conversion from nominations to winners.
The cause of this cluster and the very existence of Oscar season could be argued in many ways and could be because studios save the best for the last, or judges seem to favor the recent releases than older ones, or due to positive atmosphere during the holiday season. Whatever the cause may be, Oscar season is real and hope you enjoy this season with popcorn, family & friends.
