Depending on how much damage you've done to yourself, if you decide to whip yourself into "Summer-ready Shape" it will most likely take you at least a month.
If you give yourself at least a month you will most likely get back in reasonably good shape without doing anything drastic. If you're targeting anything less than a month, you'll most likely have to make some serious lifestyle changes, go on a severe and well-balanced professionally prepared diet, and also free up a lot of time for some low impact high intensity exercising.
If taking a more gradual approach makes more sense to you and you prefer to take 6 , 8, 10 or 12 weeks to achieve your goal, you will still achieve the SAME physiological changes but the good news is that it will be a lot easier on your brain and your emotions.
Nutrition plays a huge part of any health journey, and anyone looking to slim down for summer should start by reassessing "What", "When" and "How" they eat. I'm sure you've heard the expression "You can't out-run or out-train a bad diet"
I know people are big on cutting things out like eating dairy free or not eating carbs but I just don't think that's necessary. I can show you how you can still get great results while still eating fruit, carbs, and still eating dairy. I also believe you shouldn't have to deprive or punish yourself to achieve fat loss. You should be able to eat most things if you respect portion sizes and avoid processed foods and things loaded with sugar and salt.
The only time I would "Cut something out of my diet" is if I was told by a medical professional to exclude a certain food or food group for health reasons. The trick is..... Just eat reasonable portions of unprocessed foods and if you really want to make sure you're on the right track, ask a professional meal planner for help.