[Events +] Events+ has an issue with saving events

When using front-end posting with events+ we've started to have an issue with the front-end form. When posting an event with start and end times, we are unable to publish because it returns an error reading, "Please check your time and date settings". This is happening in all instances whenever a correct start and end time is chosen.

I've done a full round of testing already and it doesn't appear to be a theme or plugin conflict. I've already deactivated all the plugins on our development site and switched it over to a default WP theme. The issue is still present. Currently, the staging site where I am testing this through has the Twenty Fifteen theme active, Events+ and the WPMU DEV Dashboard plugin. The issue still persists.

I've granted support access to the site. The page where the front end form is displayed is here: https://staging.sactdev.net/add-or-edit-event/

The site is: https://staging.sactdev.net/