I have a very flabby body, specially the lower body is extremely flabby. Im planning on going on a healthy diet (500-800 calorie diet) and going to gym 3-4 times a week. How long will it take for me to get toned?

Um... there isn't a healthy 500-800 calorie diet that has EVER existed in the history of the human race.

It WILL make you body think there is a famine and your metabolism WILL slow to a crawl... and make it difficult if not impossible to lose weight.

And its also highly unlikely you will meet the nutritional requirements either.

That was tried once before on a large scale... In the concentration camps of Auschwitz and Dachau. It didn't turn out too well there either.

Even with a proper diet with sufficient claric content... if you are truly flabby... it might take years of exercise. A lot depends on just how out of shape you really are. Something we can't determine over the internet.

Agreed, there is no diet that only consists of 500-800 calories. If you are trying to lose weight you should still make sure to eat healthy, just cut down on sugar and fats. It also depends on the type of work outs you do. I suggest you try out a personal trainer and see how it goes.