/setdaylength {numerator}, {denominator}

Although it can be done with command blocks (albeit it doesn't work 100% how one would like it to), allowing one to make Minecraft days longer or shorter would be really nice for those that want days to last as long at an Earth day, or anything else. 

With a value of "/setdaylength 1, 2" being a fraction of 1/2, meaning the day lasts 1/2 as long, or day/night advances twice as quickly.

A value of 1/1 would set time to the standard Minecraft daylength, and if I'm correct, a simple    "/setdaylength 72, 1" would make Minecraft days be exactly as long as one Earth day.

(Fractions between 0 and 1 make the day faster, and fractions larger than 1 make it slower)

Perhaps this would also make rain/storms proportionally longer/shorter?