From the Council of Salegunstadt or Mainz, celebrated by Aribo, Archbishop of the See of Mainz, A.D. 1022

Canon III. Concerning legitimate marriages it seemed good thus: that no Christian ought to lead a wife from the Advent of the Lord up to the octave of Epiphany, and from Septuagesima up to the octave of Easter, nor in the fourteen days before the feast of Saint John the Baptist, nor on the aforesaid days of fasts (namely the four times, concerning which in Canon II), or on the nights preceding all solemn days.

Cf. Canon LII of Laodicea and the following decree of Urban II in the Council of Benevento.