# How survivors should measure time on tidal locked planet?

Setting:

Earth-like planet orbitting red dwarf.

Survivors from the Earth.

(Only one planet, not post-planet civilization like in question: How Would a Post-Planetary Civilization Measure Time? )

All typical units like day, (lunar) month or year have no longer much meaning. Needless to say local year does not have any round lenght.

If one tried to redefine second, then would face redefinging all SI units and cause serious rounding errors. If one tried to redefine year, then all historical data would start being problematic.

No longer day-night cycles, presumably the same infrastructure can be used in more than one shift.

Our contemporary way of measuring time is not specially logical:: 365, 12, 7, 24, 60... etc. It would be nice doing something with it by occasion.

People tend to react poorly if their day-night cycle departs seriously from 24h (actually studies show that average day would be a few minutes longer if one asked our biological clocks)

(the only simple thing is what to do with computers... well there would be no reason to drop unix time)

Issues to deal with:

1) Design calendar (what to keep? year? week? Round something a bit???)

2) Design a day cycle (lenght, how many shifts? 2 to allow some margin of error? 3 to perfectly utilize all equipment?)

• How fast did they get to this new world? Do they need to take relativity into account in order to maintain some relevance to Earth? Or can they just pretend time is constant because they stayed sunlight or because there's no need for Earth synchronization later? – SRM Sep 26 '16 at 23:34
• Possible duplicate of How Would a Post-Planetary Civilization Measure Time? – Thucydides Sep 27 '16 at 1:59

The base for time is likely still going to be seasons. This is especially true if you are growing food through normal agriculture. This is less true if your food is being grown in hydroponics or greenhouses.

This length is likely NOT going to align neatly with a 365 day earth calendar. The new calendar will start with a new Year One (or an actual Year Zero, if you want to avoid the weirdness of the BC / AD divide of our current calendar.

Converting between the two will become less and less important as it falls farther and farther into the past. It will just be a foot note of "A Earthyear is equal to 1.56 (or whatever) years, and was divided into 12 months instead of 5 quints."

Daily cycles will likely be set to the best cycle for humans and one-third of that will likely be a standard sleep cycle.

• There wouldn't be seasons on a planet of this type. Seasons are caused by the tilt of a planet facing different ways relative to its star, any tilt in this case faces the same way throughout it's orbit. (Assuming a circular orbit) – Matthew Wilcoxson Nov 2 '17 at 11:56

They would probably rely on earth time for quite a while as it will be deeply embedded into their computer systems. Y2K wouldn't even hold a candle to a change of this magnitude.

Time tracking on computer records is incredibly difficult to change and they would probably just rely on some sort of conversion layer. The programming code for converting years might look something like:

def new_year(old_year):
return (old_year - globals['ARRIVAL_DATE_YEAR']) * globals['OLD_YEAR_RATIO']


As for tracking years on the new planet they might be able to measure this by observing the positions of known stars in the background.

As the planet orbits the position of stars in the sky will change, you set a "new year" point and once the stars' position matches this again you know a sidereal year has passed.

With no relevant units of measurement you could use fractions of a sidereal year. Binary divisions would be a good starting point.

As for the day/night cycle I imagine society would become truly 24/7. There would be no "night life" or 9-to-5 as there is no night. Probably no seasonal work/activities as there may be no seasons due to tidal locking. Over time this would have quite a profound effect on human culture, the flow of life be fairly "steady", no rush hour etc