Upgrade breaks Rest Export View in Calendar We have a website that uses Views with a serializer rest export to display events on a monthly calendar. When we upgraded from 8.6.16 to 8.7.3 the calendar display is blank. All the json information displays in the view preview, and using console.log I can see the information load on the page. I can load events in a normal view without any issues. I've spent several days trying to figure out what change may have caused this, my leading theory is that something with date formatting may have changed somewhere, but so far, no luck. Does anyone have any documentation about a date format change between Drupal 8.6 and 8.7?

EDIT: I just noticed the difference by exporting the views preview and running a diff on them. The live site displays dates correctly like this "value":"2019-06-27T00:30:00 while the updated dev site displays dates like this "value":"2019-06-26T17:30:00-07:00" so could something have changed with time zone translations or date fields that is interfering with our code?
My edit gave me a clue to look at the date formatting. In our specific calendar instance there is an event-calendar.js file that was manually converting the dates pre-Drupal 8.7 to UTC with a .field_date_range[0].value+'+00:00',. It appears that Drupal 8.7 does this automatically, so removing that extra bit of code solved the issue and dates are being populated into the calendar correctly now. 

EDIT: For those interested, I was finally able to find the drupal documentation about this change in 8.7 here