As posted in last year's French by-elections thread, the French "overseas collectivity" of Mayotte will hold a referendum tomorrow to decide whether or not the island will become a department. The "yes" is expected to win handily, and the most important political parties all support it.
Mayotte was a part of the French Comoros until 1974. That year, the Comoros voted for independence with 95%, but 65% of Mahoran voters chose to remain part of France.
In February 1976, 99.4% of voters chose to remain French. However, that April, 97%, most of whom wanted to become a department, voted against remaining a French territory, and the island became a "territorial collectivity."
In 2000, 72.93% of voters chose to become a "departmental collectivity." Again, most of the "no" voters supported becoming a full department.
If, as expected, the "yes" wins, then Mayotte will instantly become an overseas department like Réunion, Guadeloupe, Martinique, and Guyane. However, it will take twenty-five to thirty years for the island to receive the full benefits of being a department, mostly for economic reasons.
Réunion, Guadeloupe, Martinique, and Guyane are simultaneously overseas regions (with a regional council) and overseas departments (with a general council). However, Mayotte would have a single council.
Turnout numbers and results by commune will be available here
I'm not sure at what time the polls close. I know metropolitan France turns its clocks forward an hour tomorrow, but I'm not sure if Mayotte has summer time.