As we say in the book, it’s important to find a pattern that works for you when it comes to the timetable you decide to use when eating on a Fast Day.
My method is to wake up on a Fast Day morning and have breakfast of around 300 calories at about 7am, before going to work. Then I drink lots of calorie-free fluid but go without food until 7pm, when I have a 300 calorie supper with my family (I eat the 300 calories, they tend to eat rather more).
I think of it is as ‘a day of fasting’. This makes it straightforward to explain and understand. However, as some of you have pointed out, if you eat supper at 7pm on the night before a Fast and then have a normal breakfast on the day after a Fast, you can argue that you are actually eating 600 calories over the course of 36 hours (7pm Fast Day 1 until 7am two days later).
If, however, you decide to fast from 2pm until 2pm, as some fasters do, you would have a normal lunch on Day 1, then a 300 calorie supper on Day 1 and a 300 calorie breakfast on Day 2. If you have a normal lunch on Day 2 this would be a 24-hour fast, full stop. You can, of course, decide to skip lunch on Day 2 and wait till supper to break your fast.
On the 2pm-2pm method, because your fasting window is diminished, your overall weekly calorie count will probably be higher than with the 7am-7am method. You will probably lose weight more slowly.
Some people find it hard to sleep when they are hungry and for them a 7pm to 7pm method might be easier. That way you never go to bed hungry. Again weight loss will be slower. Also, here are some great suggestions from Twitter about dealing with nighttime hunger, if you’d like to look at those. If one routine doesn’t suit you, try another. Flexibility (within the basic parameters) is key – do let us know what works for you.