Ibn Abbas (may Allah be pleased with them both) says that the Prophet (peace and blessings be upon him) was asked about the sacrifice, shaving the head, stoning, and doing things earlier or later, and he (peace and blessings be upon him) said: "There is no harm."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9624