For how many years did the Prophet (peace be upon him) pray facing Jerusalem before the Qibla was changed to the Kaaba?

There is disagreement regarding the duration of the Prophet's prayer, peace and blessings be upon him, towards Jerusalem after the Hijra. It was said to be sixteen months, or eighteen months, and it was also said to be a little over ten months. The majority opinion is that the change of Qibla occurred in the middle of Sha'ban, at the completion of eighteen months from the Hijra.