The 12 months of the Islamic calendar are Muharram, Safar, Rabi' al-awwal, Rabi' al-thani, Jumada al-awwal, Jumada al-thani, Rajab, Sha'ban, Ramadan, Shawwal, Dhu al-Qi'dah, and Dhu al-Hijjah. The Islamic calendar is lunar-based and each month consists of either 29 or 30 days, totaling either 354 or 355 days in a year.