There is some wiggle room with how you can distribute your calories for each meal while on 1200 calories a day diet, but you should try to stick to the following guidelines.
Breakfast: 350
Lunch: 350
Dinner: 400
Snacks: 100
If you don’t need snacks, you can redistribute those calories to a meal, preferably your breakfast and lunch, so each meal is 400 calories. If you are someone that does intermittent fasting, you can allocate your calorie budget to the other meals that fall within your eating window.