Saving the Mango Orchard by N. Singh

Rohan and Neel discover a magical amulet that can teleport them to a different time zone if they want to help someone. However, they have to find out a way to activate the amulet and then find a way to come back to their own time. They finally undertake a journey to meet their great grand father and help him rescue a mango orchard with the help of his pet elephant!