Thanks for davdroid. It’s a great app. Some time ago, I started using DAVdroid on two android devices, with a caldav server at https://dav.pobox.com
Today, when I installed davdroid on another android device and tried to add the same account, it kept saying, “Cannot verify hostname: dav.pobox.com” (Why? CAdroid claims that “the certificate is already trusted (locally). There is no need to import it” But anyway, that is a different topic…)
While attempting to debug the matter, I realized that davdroid was, in fact, no longer working on the devices it was formerly working properly on. logcat showed
E/davdroid.DavSyncAdapter( 5780): javax.net.ssl.SSLPeerUnverifiedException: Cannot verify hostname: dav.pobox.com
And then I realized that it had, in fact, stopped working a while ago. This is an issue because if/when davdroid fails, it should complain loudly so the user knows it has failed. Now I have a bunch of appointments created for various dates on two different devices, none of which have been sync’ed to the server. It’s going to be a pain to find them all and enter them manually into my desktop calendar program 
