Sayyidah Aishah (may Allah be pleased with her) narrates that in the time of the Messenger of Allah (peace and blessings be upon him), if one of us missed fasts, she would not be able to make them up because of him until Sha'ban came. The most fasting that he did was in Sha'ban; indeed, he would fast the whole month except for a few days.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8429