Religious Holidays - Which Ones Are Approved?

What is God's view of the many religious holidays or festivals that our nation currently observes?  What about other days that are celebrated by Jewish people like Purim and Hannukah which have Biblical origins?  Are Christians obligated to observe them?

Steven Holladay is a professor at the University of Georgia, and also serves as Department Head, Biosciences and Diagnostic Imaging. He has spoken nationally and internationally about damage to the immune system caused by endocrine disrupting environmental chemicals, and has published over 165 research manuscripts. He has been a member of numerous research journal editorial boards, was Editor of the journal Advances in Pharmacological Sciences from 2006-2009, and served as Associate Editor for BMC Pharmacology and Toxicology from 2008-2015. He has also served as an expert invited reviewer over 30 times for the U.S. National Institutes of Health (NIH) and the U.S. Environmental Protection Agency (EPA).