John was baptized June 21, 1761.
[This source says they were of Biddeford when married, may have been in Buxton "as early as June 21, 1761", which would seem to indicate that John's baptism was in Buxton, but it is not reported in Source:The records of the Church of Christ in Buxton, Me., during the pastorate of Rev. Paul Coffin, D.D. (252411). The baptisms of Jacob, Magnus and Sarah are all reported in both this source and the Buxton church records with the same date, but since John's is not in Buxton church records, I suspect it took place in Biddeford. Hence, I suspect when they say "as early as June 21, 1761", they technically mean after that date.]