Being the capital of Equestria and home of many Unicorns, Canterlot is a splenderous city renowned for its amenities and its annual, invitation-only party - the Grand Galloping Gala. It is the home of Princess Celestia and the protagonist, Twilight Sparkle.
It is here Twilight Sparkle's story begins as Celestia's senior pupil. She is promptly dispatched to the town of Ponyville to oversee preparations for the Summer Sun Celebration and to undertake what is in the Princess's estimation the most valuable lesson Twilight has yet to master - the making of friends.
When it is time for a season to end and a the next to begin, the Unicorns of Canterlot perform the changing themselves. Their innate magical abilities enable them to make all necessary changes within a day.