Prevent OSX from auto-detecting and deleting dates in iCal, Reminders
Since data detectors are handled by Mail & not iCal itself you may turn this feature of with the following command entered in Terminal:
defaults write com.apple.mail DisableDataDetectors YES
To revert this behaviour:
defaults write com.apple.mail DisableDataDetectors NO
Please note that any time detection features of Mail are turned of as well.