Aamir has had the busiest year ever. He is known for doing one project at a time, this is the first time in his career that he's been juggling his magnanimous TV show 'Satyamev Jayate' and his films TALAASH and DHOOM 3 all in the same breath. Hence the star hasn't been able to spend quality time with his family.
When he heard about the party he requested Victor (director of DHOOM 3) and producer Aditya Chopra if he would be allowed to leave a day late. Of course he didn't want to disrupt shooting or upset any schedule.
Victor and Aditya were more than accommodating and felt Aamir could join the shooting on 6th without any issues.