After doing some Calendar-related maintenance (including deleting the default community Calendar, which has been there for years, and creating a new one), I find that I am no longer able to access the Calendar app at all on my site.
When I click Calendar off my site, I get the following:
Error: Call to undefined method DateTime::getDateInformation() (0)
#0 /XXX/public_html/applications/calendar/sources/Event/Event.php(363): IPS\calendar\_Event::_findOccurances()
#1 /XXX/public_html/applications/calendar/sources/Event/Event.php(2127): IPS\calendar\_Event->findOccurrences()
#2 /XXX/public_html/applications/calendar/modules/front/calendar/view.php(178): IPS\calendar\_Event::retrieveEvents()
#3 /XXX/public_html/applications/calendar/modules/front/calendar/view.php(125): IPS\calendar\modules\front\calendar\_view->_viewMonth()
#4 /XXX/public_html/system/Dispatcher/Controller.php(118): IPS\calendar\modules\front\calendar\_view->manage()
#5 /XXX/public_html/system/Dispatcher/Dispatcher.php(153): IPS\Dispatcher\_Controller->execute()
#6 /XXX/public_html/index.php(13): IPS\_Dispatcher->run()
#7 {main}
I notice that there's a different spelling of "findOccurences" across lines #0 and #1, but everything was also working fine until I deleted my old default Calendar, so....