Other research has also shown that emojis are often misunderstood. Some of this misunderstanding is related to how the reader or viewer interprets the emoji design. In other cases, there is a technological problem. The emoji that was typed in by the writer is not shown in the same way in the e-mail received and read by the reader. This happens when the writer and reader of an e-mail do not use the same software or operating system for their devices. Emojis originated on Japanese mobile phones in the late 1990s. They quickly spread in popularity and now more than six billion of them are sent everyday around the world. There is even a World Emoji Day, which is celebrated on July the 17th every year.