Technique: Time-Lapse Video
Time-Lapse Photography is the method of capturing one frame of film at set intervals. When played back, the subject appears to animate. Typically this is done with an anchored tripod (such as with the orchid above), to capture movement imperceptible to the human brain.
Using a film camera, one frame was exposed when a timer activated the cable release, but how is this accomplished on video? Some video cameras do have a mode for this, but this is only good for the length of the tape--about 80 minutes max.
For long-term time-lapse, a camera hooked up to a computer is needed. You can use a webcam for this, but if you want higher quality video, a program like Scenealyzer Live is needed. This software (which has a free trial followed by a $39 price tag) will let you set whatever interval you want to record those long lapses, using any camera connected to your firewire port.