Diwali Celebrations on two different dates in India

Diwali is celebrated for almost a week starting from Naraka Chaturdashi to Tilsi pooja , which marks the end of the festivities. So ,it can be celebrated on any of the day within the week depending on te region. Naraka Chaturdashi was on the 29 the, Deepavavali on the 30 the and Balipadyami was the 31 st of October this year according to Hindu Panchanga, no change in that and it is fixed for that year.

Diwali beautiful and happy festival day  

Hindu festivals fall on the same date every year according to Hindu calendar which is Lunar. The dates are decided according to Moon's appearance. For example,  Diwali is celebrated on Karthik Amawasya. Karthik  being  one of the months and Amawaya being new Moon every year. We in AP celebrated Diwali on Sunday.

As far as my understanding goes, new month in North India starts from Purnima ( full moon) while in South India it starts from Amawasya( new moon). While in North India, Purnima is an auspicious day and most of the puja is done on purnima except for one puja i.e Laxmi Puja that is done on Karthik amawasya or Diwali. In south, there are people who consider amawasya as auspicious and do all auspicious things on this day. They celebrate diwali on amawasya. But there are people who do not do any puja on amawasya as they consider it inauspicious. They do Laxmi puja and celebrate Diwali a day before Amawasya or the actual diwali. 

The dates of celebration are different in South India and North India.