Kolinahr

Kolinahr is a Vulcan ritual in which all remnants of emotion are purged and pure logic is attained. The length of the ritual can vary from two to six years, or longer.

Spock began the kolinahr ritual after retiring from Starfleet in 2269. By 2273 he had completed all but the final ritual of the kolinahr, but was interrupted by the arrival of V'Ger. (TOS movie: Star Trek: The Motion Picture)

Tuvok began the kolinahr ritual after retiring from Starfleet in 2298. In 2304, during his sixth year of the ritual, he was interrupted by the onset of Pon farr, and left to marry T'Pel, his betrothed.