After the polaroid camera takes a picture, it will display the date of the photo paper in the photo, which is a unique way of photo annotation. Almost all early polaroid cameras have this function. Different from the current digital photography, polaroid camera directly exposes the film and directionally generates photographic paper on the negative, so the date of photographic paper will be automatically displayed on the negative, which is very convenient for people to clearly record the specific shooting time of each photo. This is one of the reasons why Polaroid cameras became popular in the 1950s. Nowadays, with the development of technology, polaroid cameras can achieve more shooting and editing functions, but the date mark of photographic paper has become the exclusive feature mark of polaroid, which has been loved by people.