Time dilation is a difference in the elapsed time measured by two clocks. This can happen due to a difference in velocity, or a difference in gravitational potential (clocks run more slowly the closer they are to a source of gravitation).

Theoretically, time dilation would make it possible for passengers in a fast-moving vehicle to advance further into the future in a short period of their own time. For sufficiently high speeds, the effect is dramatic. For example, one year of travel might correspond to ten years on Earth.

Examples of time dilation in science fiction:

  • House of Suns (Alastair Reynolds, 2008)
  • Interstellar (2014)
  • Star Trek: Voyager, S6E12 “Blink of an Eye” (2000)

More on TV Tropes.

Internet Time is an alternative global time system with a Y2K/dotcom flavour. It’s a decimal system which divides the day into 1,000 beats, with the first beat (@000) corresponding to midnight in CET (or BMT, for “Biel Mean Time”).

  • @000 = 23:00 UTC / 00:00 BMT / 09:00 AEST / 15:00 PST / 18:00 EST
  • @250 = 05:00 UTC / 06:00 BMT / 15:00 AEST / 21:00 PST / 00:00 EST
  • @500 = 11:00 UTC / 12:00 BMT / 21:00 AEST / 03:00 PST / 06:00 EST
  • @750 = 17:00 UTC / 18:00 BMT / 03:00 AEST / 09:00 PST / 12:00 EST

Introduced by Swatch as a marketing gimmick in 1998, it never took off as an international standard, but it lives on in nerdy pockets of the internet. (Spot the timestamp on this page.)

internet-ti.me is a convenient tool to convert between Internet Time and local time in different time zones.

With more lunar missions than ever on the horizon, the European Space Agency wants to give the moon its own time zone. That could be a challenge in a place where there are 29.5 Earth days between sunrises and clocks run faster than they do on Earth.