I'm gonna do more than 18 hours today because I'm going to bed in 2 hours and don't plan on getting up for food lol, I will eat tomorrow at 11am..If you haven't done this before, do 2 18-hour fasts a week. If you want to do Monday and Thursday, stop eating at 7pm Monday and eat at 1pm Tuesday. Do the same for Thursday. If you want to do this in an Islamic way, have suxur and break your fast with water. If the day is shorter than 18 hours, finish the rest of your fast by just drinking water. Do this for both days.