The best working combination (IMHO) is Chills Patchpack
which deals with daylength AND the unwanted side effects.
You can set the daylength factor which is a multiplier. Set it to 2 and the days take twice as long. Set it to 3 and they take three times as long.
Set it to 20 and they take 20 times as long!
Just remember that NOT everything is affected by this. Industries will produce more cargo per month... That is, in relative terms the industries will still produce X amount of cargo per real life minute. So you will still need just as many trains/planes/road vehicles/boats as before to fully service an industry.
Also, setting daylength at anything higher than 20 will have other unwanted side effects. For instance, cargo payment is divided by your daylength factor (there is a cheat to disable that though) so if you transport something very small which pays very little and it would pay like 0.49£ you get NOTHING at all. The minimum income you can get is 1£ in any currency. 1£ is "one credit" basically, all currency is based on the pound in the game.
With the cheat enabled though (do not divide income) you get paid as normal. So with a daylength factor of 10 you get paid 10x as much in a year as you normally would. It would be like playing without daylength but having more time to accumulate wealth before another locomotive is introduced on the market etc etc.