What is the ruling on fasting if the period between Fajr prayer and Maghrib prayer is approximately 18 hours?

Muslims residing in a country must fast during the month of Ramadan from the true dawn until sunset, regardless of the length of the day. As long as there are signs of night and day, it is obligatory to abstain [from food and drink] during the day. It is not permissible to consider neighboring countries or the country of origin of the sojourner. However, if night and day are indistinguishable in a particular country, then one may refer to other fatwas concerning this matter.