The Sontaran martial year was the Sontaran unit of time equivalent to Earth years.
In Sontaran martial year 5709, the Fifth Doctor interfered in the Sontaran's conflict with the Rutans on Samur. (AUDIO: Heroes of Sontar) By this year in the Sontaran calendar, Field Marshall Styre's work on human biology, conducted in Earth year 16087, was known (TV: The Sontaran Experiment) and the Sontarans had attempted to take over Gallifrey. (TV: The Invasion of Time)