It is narrated from Sayyiduna al-Harith bin Hisham (may Allah be pleased with him) that "the Prophet (peace and blessings be upon him) married Sayyidah Umm Salamah (may Allah be pleased with her) in Shawwal, and brought her to his home in Shawwal as well."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3334