Prevent OSX from auto-detecting and deleting dates in iCal, Reminders
Since data detectors are handled by Mail &amp; 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.