On Earth, we have time measured in time units that are useful only on Earth. Each planet has its own day length and its own year length.
Changing from Earth time Edit
We measure time using units that are made for Earth. The term day is set for Earth day. Its subdivisions, hour, minute and second, are also made for Earth's time. Its multiples, week, month and year, are connected to Earth's day and to Earth's year. For those that will live on other planets, this will be useless at least for their daily life.
Other day lengths Edit
Humans are made for a day that last roughly as Earth's day. We can adapt to a day that lasts a bit longer or shorter, but up to a certain limit. Based on this, we will define the following terms:
- Econimical day = the amount of time used by humans to define a day time, for their activities.
- Economical year = the amount of time used by humans to define an year time, for their activities.
- If a day lasts for 18 to 28 hours, we can adapt to it and use that day instead.
- If a day lasts for 10 to 14 hours, we can adapt by living two days as one. There will be one day for day and one day for night.
- If a day lasts for 40 to 56 hours, we can adapt by living a day as two. There will be one day during day and one day during night.
- If the day lasts for more, let's say 30 Earth days, we will use a 24 hours day for our activities. The same works for tidal locked planets.
- If the day length is somewhere between these values, we will use something related to an Earth day, but a bit longer or a bit shorter, so that after a few of our days it will match with a local day.
In the first 3 scenarios, there should also exist time zones on the planet. In the last two, there will be a single time zone for the whole planet.
As this happens, we will define the hour and the minute in a different way. Since the second is defined as an international unit for time, we should keep the second as it is.
Day multiples Edit
Each planet and moon has its own year length. We should define the year based on the planet's year, if it is something that we can compare with a human lifetime. However, in case of planets that move too slow, like Uranus and Neptune, we might still use the Earth's year. The same happens in case of planets that orbit too fast, where a local year might last a few Earth days.
As on Earth, where the term month is not quite the length of a Moon revolution around the Earth, there should be multiples of a day, composed of a number of days, also used as submultiples of the local year.
Universal time Edit
An universal time will be needed, mainly for space flights. This time, at least as long as Earth is the most important inhabited planet, should be based on Earth time units. However, it will need to be simplified. The universal time will be transformed in each local time, for each planet and moon.
The universal date will be simplified. It will consist of the year and the day of year, without specifying the month or day of week. For example: 2457, day 178. The universal time of day also should be simplified. It might be in a similar format to what we use (hours, minutes, seconds) or just a number with decimals, showing the hour (like 17.2265) or time of day in seconds (like 17445).
Ideal universal time Edit
When humans will spread across the Galaxy or in other galaxies, the Earth time will become irrelevant. We will use a new type of universal time. This time will be based on a day lasting 68400 seconds (equal with Earth's day as is now, keep in mind that Earth's day is slowly getting longer as Earth's spin rate decreases) and an year of 365.25 days. This universal time will be calculated for an ideal point that stands still in space and is not affected by gravity. The zero point will be the beginning of Earth's year zero, day zero, at 0:00:00, GMT. This theoretical year is a bit longer then Earth's real year, so that the new year's eve of the year 2000 occurred a few days later.
This universal time will be chosen in a far future, since Earth's day is getting longer and the time on Earth is perturbed by factors related to general relativity principles, which have different perturbations in other places of the Universe. As humans will spread to other galaxies, it will be very difficult to travel back to Earth to check its current time for calibration.
Transforming universal time to local time will be complicated, because we must keep in mind all characteristics of local time and the effects of Einstein's theory of relativity, which shows that time does not flow with the same speed everywhere.
Also, since many planets have elliptical orbits or are influenced by other celestial bodies, things like precession occur. This means that sometimes there should exist different hours during the year (just like on Earth we have a summer hour and a winter hour). In some places, even the length of an year is not the same.
Examples for the Solar System Edit
Here are some examples, made for the Solar System.
For Mercury, the length of a day is too long (synodic period is 115.88 days). Therefore, we can conclude that the economical day will be Earth's day and there will be a single time zone for the whole planet.
The local year is 87.969 Earth days. An year on Mercury lasts 0.240846 Earth years. So, the 2000 year new eve was in year 8304. We can use the local year, composed of 88 Earth days, but once every 32.25 local years, there will be an year with 87 days.
If someone is 30 years old on Earth, on Mercury will be 124 years and 45 days old.
For Venus, the local day is also very long, so that we should use Earth's day as the economical day. This means that there will be a single time zone for the whole planet.
The local year is 224.701 days or 0.615198 years. This means that the new year's eve of Earth's year 2000 occurred in Venus year 3251. We can use the local year, composed of 225 Earth days, but every 3.35 years, there will be an year made of 224 days.
If someone is 30 years old on Earth, on Venus will be 48 years and 157 days old.
We know well how the Earth timetable looks like.
The Moon has a day of 29 Earth days, too long to be used. Instead, we would use an economical day with the same length with Earth's day. The Moon will have a single time zone.
The Moon will use for year the length of an Earth year.
In addition, a special kind of month should be used, based on Moon's own day length and independent from the local day or local year.
For Mars, the length of a day is not too different from a day on Earth. It is 24 hours, 39 minutes and 35 seconds. This equals to 88775 seconds. We can divide a Martian day in 3 different ways:
- Consider a minute will have with 61.649 seconds
- Consider the day will have 25 hours, the last hour will be imperfect, with 39 minutes and 35 seconds
- Since 88775 has divisors 25, 53 and 67, we can use a day of 25 hours, an hour of 67 minutes and a minute of 53 seconds.
The Martian year will be 1.8808 Earth years. The Earth year 2000 occurred in Martian year 1063. The Martian year has 668.5991 local days. Using local year and local day, we will have one year with 668 days and the next with 669 days. Still, at every 10.09 years, there will be one added day (one year with 668 days will have 669).
The moons of Mars rotate too fast to use them for a month. Still, time can be divided in groups of 30 or 31 local days, which will be useful for local activities.
In addition, Mars will need local time zones. And given its elongated orbit, the difference between summer and winter hour will be significant.
If someone is 30 years old on Earth, on Mars will be 15 years and 635 days old.
Martian moons Edit
Given their small size, they will be economically linked to Mars. They will use the Martian day and year.
Ceres has a day length of 0.3781 Earth days. This means 32668 seconds or 9 hours, 4 minutes and 28 seconds. Humans might use 3 times this value as an economical day, lasting 98004 seconds. The economical day, in Earth time units, lasts 27 hours, 13 minutes and 24 seconds.
Unfortunately, 32668 is divided by 4 and 8167. We cannot divide this in a clear set of hours and minutes. Instead, we can do as follows:
- Consider a minute be made of 68.0583 seconds, we will have 24 hours with 60 minutes each.
- Consider the day to have 27 perfect hours and a small hour, of 13 minutes and 24 seconds.
The year is 4.072 Earth years or 1681.63 Earth days or 1482.519 economical days. The Earth year 2000 occurred in local year 491. A local year will be divided in 1681 Earth days (if we use the Earth day) or in 1482 economical days. From time to time, we will have years with one extra day.
Given the nature of economical day, there should not be time zones on Ceres.
If someone is 30 years old on Earth, on Ceres will be 7 years and 544 days old.
The year on Jupiter lasts 11.8618 Earth years or 4332.59 Earth days. This is a lengthy period of time, bit still it can be used for a local year. The Earth year 2000 occurred in Jovian year 168. A Jovian year might be long, but it can easily be divided into 12 seasons, each one nearly as long as an Earth year.
A day on Jupiter lasts 9 hours, 55 minutes and 30 seconds. However, since Jupiter has no solid surface, this is an average value for the rotation of the clouds. Not all cloud bands move with the same speed and two free-floating atmospheric stations will experience two different days. Inside the atmosphere, there will be probably only research missions, automated probes and helium extracting stations, most of the population will live on the moons.
What is interesting for the moons is that their revolution periods are connected. In the time when Io orbits Jupiter 4 times, Europa orbits twice and Ganymede once. This automatically means that we could use a similar economical day for all.
Local day setting. Io has an orbital period of 1.7691 Earth days. This means that, on Io, we can have two economical days in one. One economical day will last, in Earth time units, 21 hours, 13 minutes and 45 seconds or a total of 76425 seconds. How can we divide this into hours, minutes and seconds?
- 76426 is divisible with 2, 7 53 and 103. Therefore, we can have a minute of 53 seconds, an hour of 103 minutes and a day of 14 hours.
- We can consider a minute to be made of 53.073 seconds and an hour of 60 minutes, to have a day of 24 hours.
- We can still use Earth's minute and hour, but the day will last 21 full hours and an incomplete hour, with 13 minutes and 45 seconds.
Based on this, we can use the same economical day for Europa (a local day will consist of 4 economical days) and on Ganymede (where a local day will consist of 8 economical days). For Callisto, a local day is 16.689 Earth days of 18.867 economical days. A local day is too long to be correlated to an economical day, like on The Moon. The same would apply for Almathea, Himalia and all the small moons of Jupiter, which will only serve commercial or research bases and industrial centers.
We could use time zones for Io, but it looks more likely that we use a single time zone for the whole Jovian System. All other moons have a too long local day and most probably people will prefer a single time zone.
If we use an economical day based on the rotation periods of Io, Europa and Ganymede, then we will divide the Jovian year into 4898.0802 economical days. The year will have 4898 days, but once in every 12.48 Jovian years, there will be an year with 4899 days. This will be rare, once in every 148 Earth years. The year can be divided into 12 seasons, each lasting 408 or 409 economical days. Further more, a season can be divided into 12 sub-seasons, lasting 34 or 35 economical days. This will be useful for economical activities, giving something to look similar to an Earth year or an Earth month.
Earth day setting. Io does not look too habitable and might not be suitable for terraforming. The other large moons: Europa, Ganymede and Callisto rotate much slower then an Earth day: 3.5512, 7.1546 and 16.689 Earth days. It could be better to just use Earth day settings and not the local time. In this scenario, the economical day will not be linked to a local day, it will just be the official Earth day. Also, there will not be time zones. There will be a single hour for the whole system.
If we use the Earth hour, a Jovian year lasts 4332.59 Earth days. We will have one year with 4332 days and the next year with 4333. Once every 11.111 years, there will be an year with an extra day. In this scenario, an year will be divided into 12 seasons with 361 days (and occasionally 362). Each season will be divided into sub-seasons of 30 or rarely 31 days.
Complex day setting. It is possible that people on Jovian moons will use both systems. Maybe on Io and Europa they will like to use an economical day based on local day length and time zones, but on Ganymede and Callisto, an economical day based on Earth day length. In this case, Almathea might use the first time model and Himalia the second. We simply don't know.
If someone is 30 years old on Earth, on Jovian moons will be 2 years, 6 seasons and 142 local economical days (or 126 Earth days).
An year on Saturn lasts 29.4571 Earth years or 10759.22 Earth days. This is a lengthy period of time. Compared to a human lifetime, this is somewhere at the limit. Children will have less then an year, adults an year, elders two years and the oldest people will have 3 years. People could divide a Saturnian year into 29 or 30 seasons or they could simply use the Earth year. Maybe both systems will be used for a while, until one will be abandoned.
For each moon, the year will be composed of a different number of days. Given the fact that one year lasts long enough, the last day of each year will be adjusted (added or removed) to match with revolution period.
Saturn has no solid surface. Its clouds rotate with different speeds. They will only host free-floating balloon stations made for research or to extract helium.
There will be stations inside the ring gaps. In the same way, there could be stations on the ring moons. They might use local hours, the Earth economical day or the economical day chosen for a Saturnian moon. It is unknown.
Small inner moons might not use the local day.
Pan is the only exception, since it has a day length of 0.57515 Earth days, so it can have an economical day of 1.1503 Earth days or 99386 seconds (on Earth time, 27 days, 36 minutes and 26 seconds). For Pan, we can consider a minute to be made of 62 seconds and an hour of 229 minutes. The economical day will last 7 hours.
In case of all moons from Daphnis to Aegaeon, the day has intermediary values between 0.6 and 0.9 Earth days. Given the small size of these moons and the fact that they cannot be terraformed, the time used can be Earth's economical hour.
Mimas has a day length of 0.942442 Earth days (81427 seconds or 22 hours, 37 minutes and 7 seconds). Unfortunately, 81427 does not have too many divisors. So, we cannot compose a local minute and a local hour length without fractional numbers. For Mimas, there are two solutions:
- Consider a minute to be 56.5465 seconds long
- The day will have 22 full hours and a short hour, made of 37 minutes and 7 seconds.
Mimas will use time zones.
For Mimas, the year will be composed of 11415 days (30 seasons of 380.5 days each).
Methone, Anthe and Pallene have day lengths close to Earth's, but are very small. If they are economically linked to Mimas or Enceladus, they might use their local day settings or settings used for Mimas or Enceladus.
Enceladus has a day length of 1.370218 Earth days. This equals to 118387 seconds or 32 hours, 53 minutes and 7 seconds. This is too long for humans to adapt easily. Instead, we could use 3 economical days in two local days. This way, the economical day will last 0.913479 Earth days (78925 seconds or 21 hours, 55 minutes, 25 seconds). Humans can adapt to a day of 22 hours. 78925 has many divisors, so we can:
- Consider a minute of 41 seconds, an hour of 77 minutes and a day of 25 hours
- Consider a minute of 54.809 seconds
- Use Earth time units; the day will have 21 hours and a 22th hour, with 55 minutes and 25 seconds.
Enceladus might or might not use time zones. Since its economical day will not be a direct multiple or division of its natural day, it seems unlikely.
The Saturnian year will consist of 11788 economical days. They can be divided into 30 seasons of 392 to 393 days each.
Tethys has a day length of 1.887802 Earth days. This can be divided into two economical days, lasting 81553 seconds (or 22 hours, 39 minutes and 13 seconds each). In such conditions, there will be an economical day during day time and an economical day during night time.
Unfortunately, 81553 is a prime number and we cannot divide it to have round numbers for minutes and seconds. People on Tethys will have the following options:
- Use a minute of 56.634 seconds
- Use a day of 22 round hours and an incomplete hour of 39 minutes and 13 seconds.
Since the economical day will be connected to the real day, Tethys will use time zones.
A Saturnian year will last 11398.68 economical days and can be divided into 30 seasons of 380 or 379 days each.
Telesto and Calypso follow the same day length with Tethys. Given their small size, it seems unlikely they will use time zones.
Dione has a day lasting 2.736915 Earth days. This can be divided into 3 economical days, each one lasting 78823 seconds or 21 hours, 53 minutes and 43 seconds. It will be interesting. Suppose one economical day starts at sunrise, it will not last until sunset. The second day will have a sunset in the middle of the day, while the 3rd day will be during night.
Unfortunately, 78823 is a prime number and cannot be divided into round numbers. So, we cannot compose minutes and seconds based on it. We still can:
- Consider a minute to last 54.738 seconds
- Consider a day to last 21 complete hours and one nearly completed hour.
Given the nature of the economical day, Dione might not be divided into time zones.
A Saturnian year will last 11793.47 economical days, which can be divided into 30 seasons lasting 393 to 394 days each.
The small moons Helene and Polydeuces will use the same economical day with Dione, since they have the same orbital period. Given their small size, they will not have time zones.
Rhea orbits Saturn in 4.518212 Earth days. At this point, we can divide the local day into 4 economical days (lasting 27 hours, 6 minutes and 33 seconds), 5 economical days (lasting 21 hours, 41 minutes and 15 seconds) or use Earth's day. If we use the first option, during one local day we will have 4 economical days (two during day time and two during night time). For the second option, if we also consider precession (the fact that during Saturnian year sunrise and sunset will be earlier or later), people will find no correlation between real day time and the timetable. From this point of view, the third option is better then the second.
If we use the first option, the day will last 97593 seconds. This number is divided only to 3 and 32531, so we cannot divide it into round hours and minutes. So, we have two options:
- Consider a minute to last 67.773 seconds.
- Consider the day to last 27 round hours and a short hour of 6 minutes and 33 seconds.
The first option is suitable for setting time zones. The second option does not look feasible. The third one, using Earth day, will not require time zones.
For the first option, a Saturnian year will last 9525.24 economical days, which can be grouped into 30 seasons lasting 317 to 318 days each. The second option is not feasible, but the third one will have an year of 10759.22 days, divided into 30 seasons of 358 or 359 days each.
Titan and Iapetus have long orbital periods, of 15.94542 respectively 79.3215 Earth days each. They could be divided into 16 respectively 79 economical days, but this does not look feasible. More likely, these moons will use Earth day. There will be a single time zone for each moon. The year will be divided into 10759.22 days or 30 seasons of 358 to 359 days each.
It is possible that both Titan and Iapetus will use the same time zone. But even if they use a different one, they will share the same date.
Hyperion orbits Saturn in 21.27661 Earth days. However, it has a chaotic rotation, with a period of roughly 30 days. Both rotation period and axial tilt are subjects to change. Settlers on Hyperion will prefer to use Earth's day instead of any other unit. Since Titan will use the same unit for the economical day, it makes sense for settlers on Hyperion to use the same units.
Outer small moons may not be tidal locked, some of them have a chaotic rotation or not. Settlers might use in some cases economical days related to the local day, but given the fact that these moons will not sustain large colonies, it is expected that they will use Earth's hour or the hour of another moon.
Phoebe has a rotation period of 33385 seconds (9 hours, 16 minutes and 25 seconds). This moon also orbits Saturn in 550.564636 Earth days (1424.855 local days). Moreover, the Saturnian year lasts 10759.22 Earth days (or 19.542 local months or 27844 local days).
For Phoebe, a different timetable will be used. We can have an economical day composed of 3 local days (100155 seconds or 27 hours, 49 minutes and 15 seconds). We can compose the day as follows:
- 100156 is divisible with 2,2,7,7,7 and 73. Therefore, we can have a minute composed of 49 seconds, an hour made of 73 minutes and a day made of 28 hours.
- Consider a minute to be made of 69.5521 seconds.
- Consider the day to be made of 27 complete hours and an incomplete hour of 49 minutes and 15 seconds.
For humans to adapt to this economical day, it will be a bit hard at the beginning, but still possible to achieve.
Every month (revolution of Phoebe around Saturn) will be composed of 474.952 economical days. So, we can consider a month to be 475 days. However, the year will be made of 9281.33 economical days. An year will consist of 19.542 months. The year will be made of 19 complete months (lasting 475 economical days each) and an half month (lasting 256 or 257 days).
As one can see, for Saturn, we will have at least 6 different economical day lengths, time zones in certain areas and a very complex date system.
The Uranian year lasts 84.0205 Earth years. Many people will die before reaching one Uranian year. So, the economical year will be a different one, based on the Earth year. Natural years will be used only for special events (like celebrating 4 Uranian years since first humans step foot on Titania). Elders will receive a special gift when they will be one year old.
Also, Uranus has no solid surface. Its rotation period is not homogenous and anyway only science missions and helium mining companies will venture in the atmosphere. Each moon will have its own day and date system.
Small inner moons have different orbital periods. Some of them are suitable to be compared to a fraction of Earth's day (for example Portia rotates in 0.513196 days), but others don't. Even if we fix an economical day connected to the local day, there are things that will influence all. Uranus has a highly tilted axis, so that polar days and polar nights last for long. Also, given the low temperatures and low amount of energy received from the Sun, people will prefer to turn towards artificial light and artificial heating instead. So, they will make their own time tables.
On Portia, we could use an economical day made of two local days. The day will be 88680 seconds long (or 24 hours, 38 minutes and 0 seconds). 88680 does not have many divisors, so we cannot split it into round numbers of hours and minutes. Instead, for Portia we can:
- Consider a minute to last 61.5833 seconds
- Consider a day to be made of 24 complete hours and a short hour of 38 minutes.
Given the small size, Portia will not have time zones. Also, it will have an economical year as long as Earth's, made of 355.858 economical days. At every 7 years lasting 356 days, there will be an year lasting 355.
On Puck, the largest small moon, the day lasts 0.761833 Earth days. If we won't use Earth's day for Puck, we can still use 4 local days to make 3 economical days. The economical day will last 1.015777 Earth days or 87763 seconds (24 hours, 22 minutes and 43 seconds). We can divide this into hours and minutes as follows:
- Consider a minute to last 157 seconds, an hour to last 43 seconds and a day to last 13 hours.
- Consider a minute to be made of 60.94652 seconds.
- Consider the day to be made of 24 complete hours and an incomplete hour of 22 minutes and 43 seconds.
The economical year on Puck will be made of 359.577 days. So, years with 359 and with 360 days will alter.
Miranda has a day lasting 1.413479 Earth days or 122124.59 seconds. We can set 3 economical days to count for 2 local days. This way, an economical day becomes 0.942319 Earth days long, or 81416 seconds (22 hours, 36 minutes and 56 seconds) long.
81416 has not too many divisors, so we cannot divide it into round minutes and hours. Still, we can:
- Consider a minute to last 56.53889 seconds
- Consider the day be made of 22 full hours and a small hour of 36 minutes and 56 seconds.
Miranda might use time zones, but given the extreme axial tilt and the fact that economical day is not a multiple of the local day, it seems unlikely.
For Miranda, the economical year will be made of 387 to 388 days.
Ariel orbits Uranus in 2.520379 days. The best way to measure time is by setting 5 economical days for each 2 local days. So, the economical day will last 1.00815156 Earth days (87104 seconds or 24 hours, 11 minutes and 44 seconds).
87104 has not many divisors, so we cannot compose local time using round values for minutes and hours. Instead we can:
- Consider a minute to be 60.4889 seconds
- Consider the day made of 24 hours and an additional short hour of 11 minutes and 44 seconds.
Ariel will be unlikely to have time zones, given the way an economical day is set.
The economical year will last 362.298 economical days.
Umbriel has an orbital period of 4.144177 Earth days. For this moon, we can consider 4 economical days to last during one local day. So, an economical day will be 1.036044 Earth days long, or 89514 seconds (24 hours, 51 minutes, 54 seconds).
Since 89514 does not have many divisors, we cannot compose round values for minutes and hours. Instead, we can:
- Consider a minute to last 62.1625 seconds
- Consider a day to be made of 24 round hours and an imperfect hour of 51 minutes and 54 seconds.
Given the nature of economical days, Umbriel can have time zones.
An economical year will last 352.54 economical days. So, years will 352 and with 353 days will alternate.
Other moons have longer day lengths. Oberon orbits Uranus in 8.705872 Earth days, while Titania in 13.463239 days. Dividing local days into economical days is possible, but maybe settlers will prefer to use the Earth day instead.
In case of all small, outer moons, they orbit Uranus in a long timeframe. They rotate periodically or chaotic. However, given their small size, they will not be able to sustain a large colony. So, they will prefer to use other day lengths then the local day. There is a high chance settlers will prefer the Earth day.
Terraforming the moons of Uranus is a hard task, given their low gravity. If terraforming does not occur, settlers will live in domes, beneath surface or in surface buildings, but they will produce most of their light and heat. They will not be influenced by the outside world and might set their own day-night cycle. If this is the case, there is a high chance they will use Earth's day.
Neptune has a long year, lasting 164.8 Earth years. This is very long, too long for a human to live. The local year will only be used for celebrations (like two years since the first spaceship visited Neptune). The local population will instead turn towards the Earth year to use as the economical year.
Neptune is a gas planet. Without a solid surface, Neptune does not rotate synchronous. Anyway, inside its atmosphere there will only be research probes and helium mining ships.
Inner moons of Neptune have small rotation periods between 0.3 and 0.9 Earth days. They cannot be terraformed, given their small sizes. Settlers will prefer to use the Earth's day instead. However, in case of some of them, an economical day can be composed:
- Galatea has a day of 0.429 Earth days, two local days can make an economical day of 74131 seconds (20 hours, 35 minutes and 31 seconds).
- Larissa has a day of 0.555 Earth days, two local days can make an economical day of 95904 seconds (26 hours, 38 minutes and 24 seconds).
- Proteus has a day of 1.122 Earth days, which can be used as an economical day of 96941 seconds (26 hours, 55 minutes and 41 seconds).
We don't have enough data regarding the length of a day, so we cannot precisely divide a day into minutes and seconds. Also, we cannot say for sure if there will be time zones or not.
Triton, the largest moon of Neptune, has an orbital period of 5.877 Earth days. We can divide its day into 6 economical days, each lasting 0.9795 Earth days or 84629 seconds (23 hours, 30 minutes and 29 seconds).
We can divide the day in hours, minutes and seconds as follows:
- Consider a minute to be made of 62 seconds, an hour of 65 minutes and a day of 14 hours
- Consider a minute to be made of 58.77 seconds
- Consider the day to be made of 23 complete hours and a half-hour of 30 minutes and 29 seconds.
Given the way we made the economical hour, time zones will be irrelevant, so Triton will not have time zones.
The economical year will be made of 372.89 days. Majority of years will be of 373 days, with one year in 9.5 with 372 days.
Nereid has an orbital period of 360.13 Earth days (0.986 Earth years) and a rotation period of 11 hours and 31 minutes. For Nereid, we can have an economical day composed of two local days (lasting 23 hours and 2 minutes or 0.9597 Earth days). We don't know its rotation period well, up to seconds.
Nereid can have time zones.
The economical year will be in fact the month, Nereid's orbital period around Neptune. The year will be composed of 375 economical days.
Outer moons orbiting Neptune are small and will not support a too large population. They will prefer to use the Earth day and year or the timetable of Triton or Nereid.
Pluto - Charon Edit
Pluto orbits the Sun in 240 Earth years, too long to use this value as an economical year. Plutonian years will be used only for rare occasions.
A day on Pluto lasts 6.3872304 Earth days. The same happens for Charon, which is tidal locked to Pluto. We can divide this into 6 economical days, 3 of light and 3 of dark. The economical day on Pluto will last 1.0645384 Earth days (91976 seconds or 25 hours, 32 minutes and 56 seconds).
The economical day for Pluto and Charon can be divided as follows:
- Consider a minute of 43 seconds, an hour of 69 seconds and a day of 31 hours
- Consider a minute to be made of 63.872 seconds
- Consider a day made of 25 hours, plus a special hour of 32 minutes and 56 seconds.
Given the nature of an economical day and the fact that Pluto has its axis highly tilted, the use of time zones might be useless. A single time zone should be used for the whole system.
The economical year will be equal with the Earth year, made of 343.106 economical days. The year will have 343 days, but once every 9.43 years, there will be a 344th day.
Pluto's small moons will share the same time with Pluto and Charon. Given their small sizes, they cannot support a too dense population.
We already have problems with time zones. The use of multiple date, day and time zone systems will be very complicated. To see how many problems will occur, take a look at the following examples:
Football World Cup. The Football Solar World Cup finale will be played between Venus United and Rhea Athletic. The game will be held on Mars, using local time zone +7. The game will be transmitted live. I have a TV set and I live on Umbriel. When will I see the game? I need to transform local hour of Mars to my local hour, then take into consideration the time required for the signal to reach me. Also, both teams will have to adapt to Martian time zone before getting there to play.
Celebrations. When will Christmas occur? When will Easter be? How about the Muslim holidays? There might be different dates for each planet. On Mercury, the same event is celebrated 4 times, while on Jupiter, none yet. Most probably, people will try to get close dates to those on Earth. But, since the length of a day is not the same everywhere, a holiday that should be in a Sunday will fall in a Tuesday on another planet. So, people there will have to wait until it is Sunday. So, each holiday might be celebrated in different dates in different places.
Voting day. The Saturn Federation holds elections for their parliament and president. Elections are held Sunday, so that people will not be at work and will have time to vote. However, not only that there will be a different hour on each moon, but there will be a different day of the week. Elections will pass on Iapetus and in four days they will start on Phoebe. By that time, people on Phoebe will know the results on Iapetus and the elections will be influenced.
Saints. Both the Orthodox Church and the Catholic Church have saints that are celebrated in each day of the year. How will they adapt to the multitude of days and years in each area?
Clocks. I live on Mars and I have all my clocks set for Martian time. However, I decide to go on vacation on Pluto. There, I will encounter another timetable. The day will have a different length and I will not adapt fast to the new sleeping program. However, all my clocks will need to be reprogrammed. Not set, reprogrammed to the different time units found there. And I will have problems adapting to time. The hour will not have the same length, nor will the minute. All will be so confusing.
Spaceships. Even now on Earth, there are problems with cargo crossing time zones. The hardest problems occur in the Pacific, when you cross from America to Australia. You depart Tuesday and arrive Monday... Traveling with so many time units will be very challenging. Spaceships and space stations will probably use the universal time as a common unit.
Schools. At school, we are used that every class lasts an hour. But with so many hours, things will be complicated. On each planet and moon, a class will last more or less then an hour.
As shown above, measuring time will be completely different on each planet and moon. The examples are only for the Solar System, but similar problems will occur everywhere humans will go.