Why did the makers push back the release of P.K

Aamir Khan, Anushka Sharma, Sanjay Dutt and Sushant Singh Rajput starrer P.K. was all set to hit the screens in June this year. Since its coming together of Khan and Hirani after 3 Idiots, we were really looking forward to their latest offering. But sadly the makers of P.K. changed the release date of their film from June to December.