It is essential to make the intention to fast the month of Ramadan at night before Fajr. It is not sufficient to start fasting during the day without the intention.

If a person starts fasting in one country and travels to another where Ramadan began later, they must continue fasting until the local community observes `Eid. This may result in fasting 31 days. However, if they move to a country where Ramadan ends earlier, they should break the fast with the locals and make up missed days later.