Dan Provost on Apple’s time-lapse photography feature in iOS 8:
The result of this method is that anything you shoot will generally end up being between 20 and 40 seconds long, an ideal shareable length. Also worth mentioning, the resulting video is always 30 fps, the standard framerate for video. No surprises there.
It’s pretty clever how Apple built their time-lapse mode — working to keep the resulting video files short and shareable while also helping to keep these videos from filling up available storage space on your iPhone too quickly.