If you are asking about a specific software feature that generated this video:
If you saved a Live Photo as a video, it often adopts a timestamped name similar to this. 3. Contextual Content Video Dec 21, 10 09 54 AM.mp4
In many years, December 21 is the Winter Solstice; the video might feature specific lighting or astronomical events related to the shortest day of the year. If you are asking about a specific software