Comment by returnorthrow

You’re likely referring to SMPTE timecode, a method of conveying timing information about a video signal (eg. HH:MM:SS:FF), which is SMPTE 12M. There are various ways that timecode is conveyed in media such as LTC (linear timecode, usually carried as an audio signal), VITC (vertical interval timecode, in the vertical blanking interval of a video signal), and others.