Short Work mod changes every job to take half the normal work time. It does not change days of work, payment for work or when the work starts.
Remember that game progress is still the same and the game rewards you for finishing work. So it does not take twice the time to get promotion at work with this mod.
To install this mod, unpack the package file somewhere and place it in the 'My Documents/Electronic Arts/The Sims 4/Mods' directory.
Warning! If you are using any other mod that changes days of work, payment or when the work start, there is a high chance that this mod will conflict with others!