Mobilizon.Service.DateTime.fallback_tz

Called by:

• Mobilizon.Service.DateTime.calculate_next_day_notification (L82)
• Mobilizon.Service.DateTime.appropriate_first_day_of_week (L152)
• Mobilizon.Service.DateTime.build_notification_datetime (L177)
• Mobilizon.Service.DateTime.is_between_hours? (L189)