Sayyiduna Abu Bakrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Two months of Eid do not fall short: Ramadan and Dhu al-Hijjah."
The meaning of the hadith, and Allah knows best, is that even if they come out as twenty-nine days, they are complete with respect to the rulings connected with them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8203