If a date is present in the filename (e.g. in YYYYMMDD format) or Exif data, it will be automatically set as the day the photo was taken. Otherwise, it will be set as unknown.
Note: File uploads are logged to prevent abuse. Exif data is removed from photos when uploading. By adding a photograph, you certify you have taken or have the right to use the image you’re uploading, and that you’re OK with it being displayed in this archive.