I found this really fun site - http://www.earthcalendar.net/index.php. It's called Earth Calendar and every day you see what holidays are being celebrated around the world. For example, today's holiday celebrations include:
China: National Youth Day
Netherlands: Remembrance Day
Namibia: Casinga Day
Denmark/Greenland: Great Prayer Day
You can look up holidays by date, country, religion, and lunar phases. Have fun with it and learn what holidays are happening around the world!