Dropbox has a 'Camera Upload' feature, that allows you to upload photos and videos automatically. If you upload photos by using Camera Upload, then it automatically changes the names of your photos. It will reflect to the date and time they were taken like 2015-01-22 10.16.30.jpg. Dropbox does this, because many mobile devices and cameras will name photos with sequential numbers such as IMG_001.jpg, IMG_002.jpg, IMG_003.jpg. This will cause problem if those numbers are used again for different photos. You will cause problem when you start using a new camera or SD card. That's why Dropbox gives your photos unique names by changing the name of each photo to the date and time.