What do u mean by advert calender and where do we find this calender and what is the use of it..can anyone guide me

Advert Calendar is where you can get pokemon (normal or Shiny pokemon only), items, Points, Money and Coins by click on the box that match matches the date.

If I remember right the link to the Advert Calendar will appear near the top left side under the Main Menu.

On each Day you will click on the Box that match the number of that day, for example if the Date is December 8, you will click on the box that said 8. the box will open to page and say you receive neither a Pokemon, Points, Coins, Item or money.