Dictionary.com Word FAQs
Which is correct - Veterans or Veterans' Day, Presidents or Presidents' Day, Valentine's Day or Valentines' Day?
If the holiday is for veterans (plural), then it is Veterans' Day. If the holiday is concerned with past presidents (plural), then it is Presidents' Day. But if the holiday honors Saint Valentine, then it is Valentine's Day. However, many dictionaries say it is ok to write Veterans Day with no apostrophe. The main question is possession; does the holiday belong to a singular or plural entity? If you are unsure, check the dictionary that you use for most of your work.