Hi,
I made a particle simulation, remmaped its time to make it slower, rendered it overnight into .png sequence, then realised it was not finished i stopped rendering, changed start frame number, saved, closed blender, did my daily job, then at the end of the day opened blender, and “resumed” the rendering. Next morning I realised that the two parts don’t match 
it loox as simulation was recalculated the for the other part. Am I doing something wrong?
I suspect that time remapping could be the slippery part of the equation.
Is there a better, easier way of slowing down the scene so I can make simple slow motion animation?
Thanks!
Creating slow motion is accomplished by remapping the old and new time in the render panel under the framerate. If you set it to 30/60, you should get a decent slow motion effect.
Did you remap the particle system time by changing values under the Render Context (TAB)?
If so, you may want to slow down your particle system by leaving time remap alone and changing the Timestep (under the Physics rollout) of the particle system instead. It defaults to 0.04, set it very low, like 0.001. This way other parts of your animation are not slowed down, only the particles.
Also remember to set your cache step to 1, it defaults to 10. If you know you want to resume a render you may also want to Bake your particles that way the data is written to a disk file and not calculated on-the-fly.