The Vulcan calendar was the system of time measurement used by the Vulcan people. The calendar did not use the time of Vulcan's orbit around its sun as a basis, but instead used the period of an orbital resonance with the planet's sister world, T'Khut, as the basis of one year. This meant a Vulcan year was 266.4 standard days long. Gariff Lucsly once repaired a Vulcan clock because the intricacies of Vulcan time measurement intrigued him. (DTI novel: Watching the Clock) One of the Vulcan months was called Ailat (ST reference: Federation: The First 150 Years).