If you’re building a list of holidays for your local business – to celebrate events, or plan which days to be closed, or temporarily change your website banner accordingly, or promote a seasonal sale – a list of local culturally recognized holidays is probably fine. No one will care if mom and pop’s central Iowa pet shop website, designed for and catering to local patrons, doesn’t recognize, say, Nemzeti ünnep (the Hungarian national holiday).
But if you’re a global organization looking to make sure your product delivers relevant experiences to global users…you probably need something a little more substantial, complicated, and tuned to the cultural norms of your audience (really: audiences, which is the point).
Let’s say I sell greeting cards online: you can search for, personalize, and print out greeting cards for various occasions. Sounds simple, right? But if you have a truly global reach (mine is a very ambitious greeting card website), you need to offer your website and content in different languages…depending on where your users are, maybe a LOT of different languages.