They fasted then they went back to their homeland where Ramadaan had not yet begun
Question

                My question has to do with whether it is obligatory to fast when there is a difference in moonsighting between two countries. We left Saudi territory after it was proven that the month of Ramadaan had begun, and entered Jordanian territory – where we live – after Zuhr on that day, and it had not been proven that Ramadaan had begun in Jordan. Many travellers did not fast on that day, because they did not know of the shar’i ruling concerning that. What is the ruling? Should they make up the fast for that day? With regard to the travellers who did fast on that day, is their fast valid, and should they complete the fast in Jordan even if the number of days that they fasted turns out to be 31 days?.
Praise be to Allah.
    Firstly: 

    In the answer to question no.
    50487 we stated that the sighting 
    of the moon may differ, so each country should fast according to its own 
    sighting and they do not have to start fasting when the moon is sighted in 
    another country. 

    Secondly: 

    It seems – and Allaah knows best – that if Ramadaan begins 
    when a person is in one country then he should fast with the people of that 
    country, even if he is travelling on that day to another country where the 
    beginning of the month has not yet been announced. That is because fasting 
    that day became obligatory for him when the month of Ramadaan began when he 
    was in the first country, because Allaah says (interpretation of the 
    meaning): 

    “So everyone of you who is present during that month 
    should spend it in fasting”

    [al-Baqarah 2:185]

    This person was present during the month so he has to fast.  

    With regard to the command to count the number of days of the 
    month, and the difference of opinion as to whether Ramadaan should be 
    completed according to the reckoning of the first country, or according to 
    the reckoning of the country to which he travelled, the basic principle that 
    is mentioned by many of the scholars concerning this matter is that the one 
    who travels to another country should follow the ruling of the country to 
    which he has come, as it says in al-Majmoo’ by al-Nawawi (6/274). If the 
    people in the second country complete the fasting as thirty days, he should 
    fast with them, even if that means that he will have fasted thirty-one days. 
    But if they fast for twenty-nine days, there is no problem in that case, 
    because then he will have completed thirty days, and the month may be 
    twenty-nine days or thirty days. 

    Al-Nawawi (may Allaah have mercy on him) said in 
    al-Majmoo’ (6/274): 

    If he started to fast in one country then he travels to a 
    distant country where they did not see the new moon when the people of the 
    first country saw it, and he completes thirty days from the time when he 
    fasted, if we assume that each country has its own ruling, then there are 
    two points of view, the more sound of which is that he has to fast with them 
    because he has now become one of them. 

    What if he saw the new moon in one country, and celebrated 
    Eid with them, then he travelled by ship to another country and finds the 
    people there fasting? 

    Shaykh Abu Muhammad said: He has to refrain from eating and 
    drinking for the rest of that day, if we say that each country has its own 
    ruling. End quote. 

    It says in Tuhfat al-Muhtaaj (3/383) that Ibn Hajar 
    al-Haytami (may Allaah have mercy on him) said: 

    If we do not say that the people of the other country have to 
    fast because of the differences in moonsighting, when a person travels there 
    from a land where the moon was sighted, the more correct view is that he 
    should join them in fasting until the end of their month, even if he has 
    already completed thirty days, because by moving to where they are he has 
    become like them. End quote. 

    It says in al-Insaaf, which is a Hanbali book 
    (3/273): 

    It says in al-Ri’aayat al-Kubra: If he travels from a 
    land where the moon was sighted on the night before Friday to a land where 
    it was sighted the night before Saturday, and he has completed a month of 
    fasting but they have not sighted the new moon, he should fast with them. 
    End quote. 

    We have previously quoted on this site many fatwas from 
    contemporary scholars which affirm this ruling.  See the answers to 
    questions no. 38101,
    45545 and
    71203. 

    From the above it may be understood that the one who fasted 
    and completed the fast on the first day of Ramadaan did the right thing, 
    because you were in a country where the sighting of the moon had been 
    confirmed for that day, so you were obliged to fast then, even if you 
    entered your own country – where no announcement of Ramadaan had been made – 
    during that day. 

    Then when you travelled to your country in which the fasting 
    began a day later than in the first country, you should continue fasting 
    with the people there, even if that means that the number of days you fast 
    is thirty-one. 

    And Allaah knows best.