Messenger of Allah ﷺ vowed to keep aloof from his wives for one month, and he had dislocation of his leg. So, he stayed in a Mashruba for 29 nights and then came down. Some people said, "O Messenger of Allah ﷺ! You vowed to stay aloof for one month," He replied, "The month is of 29 days."
آلَى رَسُولُ اللَّهِ ﷺ مِنْ نِسَائِهِ وَكَانَتِ انْفَكَّتْ رِجْلُهُ فَأَقَامَ فِي مَشْرُبَةٍ تِسْعًا وَعِشْرِينَ لَيْلَةً ثُمَّ نَزَلَ فَقَالُوا يَا رَسُولَ اللَّهِ آلَيْتَ شَهْرًا فَقَالَ إِنَّ الشَّهْرَ يَكُونُ تِسْعًا وَعِشْرِينَ