ِAbout Event ?

New events usually come with new content(patch/update).
All new events are posted in this section.
http://forum.z8games.com/forumdisplay.php?7-CrossFire-Announcements
You can also follow their Facebook page to get notifications about new events and announcements.
https://www.facebook.com/crossfireonline/?hc_ref=PAGES_TIMELINE
Also launcher shows new events as well. Just click on any of the banners, and it will lead you to the specific thread in the announcements section.

There are in game banners as well, but most of the times they're outdated. So, you shouldn't count on those.
You should check either announcements section or Facebook for new events in general. The launcher doesn't show some events sometimes.