iCal sync issues with iPhone, iPad and MacBook

When troubleshooting iPad/iPhone sync issues with your MacBook (or whatever) running OS X 10.6.8, this will help you:

defaults write iCalExternalSync debugLevel full tail -f ~/Library/Logs/iCalExternalSync.log

It still took quite some time to spot the duplicate (exception-) dates in recurring events, but deleting them manually, re-synching and adding afterwards did the trick. Not sure where this duplicate dates came from, but I suspect that it has something to do with timezone support being off by default in iCal.