In the IGI, there are two John Harlands who would be within the age range to have married Mary Langdale. They are John, son of William and Susannah (sister of Mary who married John Langdale) and John, son of Michael
John Harland, M, christened: 15 Dec 1762, Leake, Yorkshire, England, Father: Willm Harland, Mother: Susanna.
John Harland, M, christened: 21 Apr 1771, Leake, Yorkshire, England, Father: Michael Harland, Mother: