Is it possible to change recorded keynote timing after recording manually? Is it possible to change the timing manually of recorded keynote presentation instead of having to re-record the whole presentation because of one error?

Sometimes when I record a keynote presentation to my audio it can happen that on one slide I make a mistake of progressing to early with the animations, so it can be very discouraging having to record the whole presentation again only because I missed the timing on some slides.

I suspect that keynote saves somewhere the time codes for when to progress to the next animation, because when exporting to a quicktime it seems that keynote has actually to run and record the whole slideshow again
You can't do this in Keynote.  Keynote recording only allows for you to record the whole narration at once.  You could work around this by recording your audio in GarageBand, and then importing your GarageBand audio into Keynote.  GarageBand allows for much more finely-grained control of your recordings, including re-recording a section.  

Another option is to use PowerPoint:Mac, which does allow you to re-record the audio for one slide.