Dr. Zakir: According to the hadith of our beloved Prophet Muhammad (saws) it's mentioned in Sahih Hadith of

Tirmidhi in the book of Fasting hadith no. 697 the Prophet (saws) said:
"Start your fast with the people who are starting the fast"

Means if you live in a country or live in a place if those people are fasting you should fast and break your fast when the people around you, when they break the fast"

So if he lives in Saudi Arabia, he should start his fast with the people of Saudi Arabia, if in between in Ramadhaan if he goes back to his original home in India then he should fast till the time his people are fasting and I'm aware that many a times there's a difference of a couple of days so if he starts his fast two days earlier and he goes to India by the time he finishes his thirty fasts the people of India may yet have a one or two fasts left. But yet he has to continue fasting till the people of India even though it exceeds more than thirty days it may be thirty one sometimes thirty two days because the hadith says that fast with the people who are fasting around you and break the fast with the people who are breaking the fast around you but if it's the vice-verca if he starts the fast earlier two days late and then comes to Saudi Arabia then maybe he'll fast 28 days in this case he has to start with the people of India end with the people of Saudi Arabia and he cannot fast on the Eid day because it is Haraam but after that he has to atleast fast one more day because in any lunar month is 29 days. He should atleast fast additional one or two days to make up for 29 or 30 days so that it doesn't mean that he has fasted less than the minimum requirement.