Time out of Time

When I decided that I was going to write the sort of story that spanned dozens of planets spread around our galaxy, I realised that I’d need to do something about time and calendars.

Because no two planets will have the same length of day, or for that matter year, I needed to come up with a way of sorting it all out so that clocks and watches would do something vaguely useful. This is the solution:

She (Jane) glanced at the map on the screen of her personal, and chose, almost at random, a spot called Baie des Poissons. ‘Fish Bay,’ she said to herself. ‘I hope that means they catch fish, or at least eat them.’

Three hours later Jane was installed in a little cabin at the back of the broad sandy beach, and was wondering how best to enjoy herself.

She glanced at her watch, then reset it to show only four-time—local solar time in hours and minutes. Six-figure atomic accuracy and interplanetary correlations could wait until she was back on duty. “Getting on towards time for dinner” was all the precision she needed at the moment.

Planets are only considered for colonisation if they have a length of day that’s within about ten percent of Earth’s. That means roughly twenty one and a half to twenty six and a half hours. Also the length of their year has to be between twelve and eighteen months by Earth’s calendar.

The length of a second is exactly the same everywhere, and is measured by atomic clocks. “Six-time” is hours, minutes and seconds using sixty second minutes, sixty minute hours and twenty-four hour days. Any clock with a second hand or displaying seconds as digits is on six-time. It’s the same everywhere in the galaxy, so if I’m on Greenworld looking at a lovely carved wooden clock with a second hand, and talking on Starline to you while you are having a drink before lunch in the Tharwa Grill on Canberra, looking at a chrome and glass six-figure digital clock, we’ll agree about the time. Stopwatches also use six-time, so if you time someone running a hundred metres through the Greenworld equatorial forest, and I time someone putting in a hundred meter sprint on the Savernake beach, we’ll know which is faster.

This isn’t very useful for times of trains or knowing when the restaurant opens, so for that sort of thing there is four-time. With four time, which is used by clocks without seconds hands or seconds digits, the length of a minute is adjusted to suit the planet that the clock is currently sitting on. With watches this happens automatically, as you get off a spaceship you watch picks up the local wireless net and resets itself. There are always 60 minutes in an hour and 24 hours in a day, but the length of a minute can be anything between 54 and 66 seconds by the standards of Earth. You can still have an 8:14 train that gets you to the office before 9:00, even if the next day isn’t 24 hours later.

I’ll talk about calendars in another post.

Leave a Reply