Time conduit

Time conduit is an incredibly rare, powerful spell that allows the creation of a very short-lived portal backwards through time. It causes items that are anachronisms in the destination time to be removed, only restored into existence on the bearer's return to his or her own time. Pages from spellbooks or scrolls that refer to spells not yet in existence become blank, only being restored if the bearer travels forward in time again. It is possible for the caster to decide upon the destination time and culture, and this can potentially create the other end of the portal at any rough location the caster chooses.

Drawbacks
The spell causes those travelling through the portal to age by one year, but their stay in the alternate time cannot last more than thirty days. The portal will always take the time travellers to the first day of the destination year, and will always return them on the last day of the original year. Beings cannot exist in two places at once on the timeline, so it is impossible to travel to the same destination time twice, and an attempt to do so will cause the spell to fail catastrophically.

Materials
In order to cast the spell, the caster must possess the scales of three dragons, one of each alignment. He or she must also possess the dust from a dead time elemental, and some soil or stones from the destination time. The caster must also have researched the destination time to gain a thorough knowledge.