I am getting an error when saving an event.

"A non well formed numeric value encountered" on line 573 of C:\Websites*****\vendor\nesbot\carbon\src\Carbon\Carbon.php

(starred out the website name)

Unable to reproduce this on Linux server. Please provide more of the stack trace info if you can.

I found that Event form in backend was broken by recent changes made to October timepicker widget.
This caused errors in Occurrence creation and also caused a Carbon error. IT has been fixed now.