What is the ruling for one who fasts before or after his country if the month differs?

The Shaykh : This person is asking, saying that he came from Egypt and that we fasted one day after you. So if the month was short, what is the ruling? Do we break our fast with you? People ask about this a lot, so we say: if the month was completed for us at thirty days, then they fasted twenty-nine days, so they break their fast with us and they owe nothing. And if the month was twenty-nine days for us, they break their fast with us as well and they make up one day. And the reverse: if someone traveled from Saudi Arabia to Egypt and the month was completed for them, he will fast thirty-one days, because the Prophet (peace and blessings be upon him) said May Allah bless you. Now, the questions will come, if Allah wills. Nader, you and Adel, tomorrow, if Allah wills. It is required if it is less than twenty-nine. It is sufficient for the month to be twenty-nine. But the sighting was established for them and they broke their fast together. If we fasted thirty, it is twenty-nine for them.