What are the durations of strokes and events in a 4-stroke engine?
The duration of the stroke is simply the time the piston takes to run from the bottom to the top of the cylinder or vice versa, half a rotation.  So if the engine is running 2000 rpm, or 33.33 revolutions per second, or 16.66 strokes per second, the stroke duration is .06 seconds, half of one full revolution.

That's the physical mechanical stroke.  However the "events" overlap the strokes.  Ignition on an aircraft piston engine starts normally around 24 degrees before Top Dead Center, so the power "event" actually starts before the compression stroke is completed.  Same with exhaust; the exhaust valve may open slightly before the power stroke is complete (piston not quite at bottom dead center) and the intake valve may open just before exhaust stroke is complete. 

This is all done to take advantage of inertial effects of the mass of the air fuel charge.  There is a lot of overlap of all these events with the mechanical stroke and is a function of valve and ignition timing, so for a given engine you need to look at a diagram of the timing points for ignition and valve opening/closing for that particular engine.