Nightly Lightning builds are available for development and testing * There are KNOWN BUGS in the calendaring code, some might cause DATALOSS. o Don't trust these builds with important calendaring or mail data o Always make backups (one possible strategy for Calendaring data backups is described at Calendar:WebDAV testing harness). * Please report bugs at http://bugzilla.mozilla.org/ Compatibility In case you are not sure which version to download, please check the Calendar Versions page at https://developer.mozilla.org/en/Calendar/Calendar_Versions.