h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Would it not make sense to make time decimal. Would it not make it easier for mental arithmetic?

It would be useful in that our time system would then match our counting system, but the time system is quite useful. 24 can be divided by 2, 3, 4, 6 & 12 whereas 10 can only be divided be 2 & 5.

So it'd be better to move over our counting system to 24 (or 12).

Firstly, just because you're used to decimal (base 10) doesn't make it easier.

Secondly, decimal time already exists, it is sometimes labeled Internet Time. Swatch have a range of watches which feature it, they have more information here: http://www.swatch.com/alu_beat/index_section.php

Theoretically, the length of a day (the Base unit of measurement - which is directly related to one rotation of the earth on its axis) COULD be divided into decimal "hours" and parts thereof. However, unlike other units of measurement (length, weight, volume, money etc.)with their decimal base units of metre, kilogram, litre, pound or dollar etc., Time has TWO base units - the Day and the Year (orbit of the earth around the sun) - which can not be easily related to each other decimally. Get what I mean? You could divide up a Year into decimal "months" and you could also divide up a day into decimal "hours, minutes and seconds". But you can not divide a year into a nice round decimal number of days.

You could if you attched rocket blasters to one side of the Earth and pushed it in or out a bit...

The SI unit (I think that's the right term), that is to say the unit used in equations by scientists, for time is the second. Considering that there's 86400 of them in a day, getting a nice decimal day isn't much of a likelyhood without either not using them (and thus having the scientista using a unit no-one else does) or mucking about with a lot of scientific constants, that have been in use for years (and possibly coming up with a few new ones).