Question: If a person continues the Sawm (Fast) of Ramadaan for thirty days, will he be obliged to abide by the Sawm he started in Saudi Arabia according the sighting of the moon of Shawwal in the Kingdom even after his arrival in India? Or should he continue Sawm with the Muslims there and fast 31 or 32 days? If he breaks his Sawm during the interval days on his journey, is he obliged to make up for the missed days after `Eed-ul-Fitr (the Festival of Breaking the Fast), or it is enough for him to fast these days with the Muslims in India after his arrival there? Kindly, give us your Fatwaa’. May Allaah reward you, and provide you with good health!
Answer: A person should start Sawm according to the country from which he sets out and ends it according to the country to which he travels. If the total number of days that he fasts is twenty-eight, then he must make up for one day, because the lunar month cannot be less than 29 days... read more here.