Carl Cushman, a college professor, age 58, purchased and moved into a house on August 1, 2017. He used the house continuously until September 1, 2018, on which date he went abroad for a one-year sabbatical leave. During part of the period of leave, the property was unoccupied and it was leased during the remainder of the period. On October 1, 2019, one month after returning from such leave, he sold the house. Can Carl use the exclusion for the sale of residence?