Harp of Ages
Found in Nayru's house, the Harp of Ages has three different songs which allow you to travel through time. Tune of Echoes - awakens Time Portals, allowing you to travel between the past and the present. Taught to you by Nayru after finding the Harp of Ages. Tune of Currents - transports you from the past to the present, leaving a portal to go back to the past where you used it. Taught to you by a researcher near Symmetry Village in the past.
Tune of Ages/Time - allows you to warp back and forth between the past and present freely. Taught to you by Nayru after you free her from Veran.