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Timekeeping in the Third Imperium

This article originally appeared in the November 2013 issue.

When we speak of time and timekeeping in the Traveller universe of the Third Imperium, we are really speaking about three different things, because there are three different ways that time can be measured:

We’ll consider each of these in turn, and how they are handled in the Traveller context by the Third Imperium.

Measuring Elapsed Time

Many scientific and engineering processes require precisely measuring elapsed time, and communicating those measurements accurately to any reader, regardless of what world that they are on. For example, cupcakes take 20 minutes to bake, whether on a ship in deep space or on any planet with a standard atmosphere, regardless of the planet’s rotation or orbit. Since many life-critical processes depend on these measurements, this is a safety issue: regardless of who is speaking or who is listening and on whatever world they are on, “20 minutes” or “3.2953 seconds” must mean exactly the same thing, with no conversion required.

So, the Imperium defines the base unit of time as a “second” with an easily-repeatable physical experiment that defines its duration. For example, it might match the current Earth definition of “9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom”. This sort of definition is easily repeatable on nearly any TL-6+ world and yields consistent and accurate results. From this, the Imperium can then define minutes (60 seconds), hours (60 minutes), days (24 hours), weeks (7 days) and years (52 weeks plus 1 Holiday day) as larger units of time.

Time on Multiple Worlds

Any interstellar government requires a way to communicate specific times without referencing any particular world. For example, an admiral may need to write orders to direct ships that might be in multiple star systems to rendezvous at a particular time. There needs to be a consistent way to refer to time in that order - and one that isn’t open to different interpretations based on what star system the author or recipient happens to occupy.

With the framework of time units from seconds to years already established, all the Third Imperium really needs to do is set a starting point, and count time from there. Year Zero is the starting point, and the Imperial Office of Calendar Compliance is responsible for enforcing both the definitions and the starting point across all of Imperial space. This is Imperial Standard Time; all Imperial ships and facilites, and most civilian starships and deep-space facilities use it exclusively.

There is even a standard nomenclature for dates and times: dates are typically written as a three digit day number and a four digit year number, separated by a dash. IMTU, either the 039-1107 or 1107-039 format is acceptable; for some applications the latter is preferable, since it can easily be sorted into date order and can be prefixed with a negative for events that predate the Third Imperium. Time is written as colon-separated hour and minute, with optional seconds and decimal seconds (e.g., 00:16 or 00:16:32.40).

Local Timekeeping

The need for local timekeeping varies considerably with the conditions on each world. Worlds like Aramis or Glisten, where all of the inhabitants live in man-made habitat areas, will probably just keep Imperial Standard Time. However, worlds where the inhabitants spend a lot of time in natural environments, and particularly worlds where the planet’s rotation is close enough to the standard day for humans to synchronize with its cycle, will need some way of keeping local time.

Most worlds use a system based on the planet’s rotation and orbit to keep track of local time. Terms like “hour”, “day”, and “year” aren’t used, to prevent confusion with Imperial Standard Time, so terms like “rotation”, “sol”, or “bright” are in common use for the local day, while “orbit”, “trop”, “anno”, or “cycle” are often used for the local year. Additionally, local terms in local languages may be used, such as drandir on Vland.

For most ordinary purposes, time resolution (that is, how finely time intervals are divided) on the order of a minute are adequate, so it’s not uncommon for local timekeeping to simply divide the local rotation period into 1,000 parts (yielding intervals generally in the one-to-two-standard-minute range), and count them from the local customary starting point. This is especially common where Vilani culture is strong, but it is considered unremarkable essentially anywhere. Regardless of what the intervals are called, times using this scheme are conventionally written as “@” followed by the number of intervals since the start of the rotation (e.g., @500 is half of a rotation, @750 is three-quarters, and so on). Time zones, where used, can be indicated by a positive or negative offset following the time. Progress through the orbit is measured in terms of local rotation, and the conventional notation described above can be extended to include the number of rotations since the beginning of the current orbital cycle. So, for example, slightly before the halfway point during the 243rd rotation of the orbit might be @243.479.

Longer periods of time can be represented by the number of orbits from a defined reference such as a key historic event (e.g. 1972@243.479). Although orbits may not be an integral number of rotations, local dating typically treats them as such, and adds intercalary rotations at intervals to resynchronize.

Because of this uniformity of timekeeping structure, it is easy to manufacture timepieces that can be customized for a particular world by inputting the orbital period, planetary rotation, and reference point in Imperial Standard units, and such timepieces are routinely available on worlds of TL7+. Many are dual-display, and show both the current Imperial Standard Time and local time. Lower costs may be achieved by omitting the ability to reprogram; many non-travellers take this option. At the other end of the spectrum, wealthy travellers may have watches that can automatically reset and reprogram from starport data broadcasts.