Gate of Time

The Gates of Time are a pair of gates that appear in Skyward Sword. They are capable of creating a portal through time to travel to the era just after Hylia's fight with Demise. Its appearance is like that of a massive clock gear being spun by two gears in either upper corner. The symbols of Din, Farore, and Nayru are upon its glassy surface, and the Triforce is in the center. A spiral of hollow, blue gear shapes appear when the gate is open and the glassy surface reappears when it is closed.

History
The first Gate of Time Link encounters is in the Temple of Time in the Lanayru Desert. Impa and Zelda are about to enter its threshold when Ghirahim appears and attacks. Link intervenes after Impa is overwhelmed by Ghirahim's power and Zelda entrusts the Goddess's Harp to him just before they both escape, destroying the Gate of Time behind them.

Link travels to the Sealed Grounds where the old woman reveals the existence of a second Gate of Time. Ghirahim learns about the second Gate of Time from a drawing in the Fire Sanctuary. To activate it, Link must temper the Goddess Sword into the Master Sword by obtaining the three Sacred Flames hidden in the Faron, Eldin, and Lanayru provinces. Eventually Link is successful in this endeavor, though his efforts necessitate resealing The Imprisoned on multiple occasions, and meets Zelda in the distant past. After she enters a deep slumber, Link uses the gate again to return to the future and quest after the Triforce. He uses the gate during this mission to plant the Life Tree Seedling in the past and recover the Life Tree Fruit in the present to revive Lanayru.

After Link wishes upon the Triforce for the destruction of Demise in the present, Ghirahim abducts Zelda and takes her through the gate in an attempt to revive Demise in the past. Link and Groose follow through the gate to rescue Zelda, and after they succeed, they use the gate a final time to return to the future.