Seasonal collections have been offered since close to the game's release. Although there is currently no way to get the products once the seasonal quest is over and the "expired" popup is crossed out, the developers have not ruled out a sale on "last year's" fashions after a seasonal collection is one year old. It is one of 21 Styles in the game.
Completing the Quests
Each Seasonal Quest series has 4 steps with 4 quests each, comprising a total of 16 quests. Generally, each quest also has 3 tasks, making 48 tasks in total. There are 4 products offered in each Seasonal Quest series, and you win one for each step you complete. You can see a preview of the products by clicking on Marco and scrolling through the Seasonal Quest window.
In the example on the right, the player has completed steps 1 and 2, but still has two steps to go. They have 9 days left to complete these quests before the products are only offered by purchasing with Diamonds.
The right and left scrolling arrows allow you to see what you have won already (left) and what is left to win (right).