Calendar view and card do not use 24h "Time Format" from profile

[jesperll]

Checklist

• I have updated to the latest available Home Assistant version.
• I have cleared the cache of my browser.
• I have tried a different browser to see if it is related to my browser.

Describe the issue you are experiencing

When setting Profile Language to English and Time Format to 24 hours the calendar panel and card show events using AM/PM

Describe the behavior you expected

I expect the calendar views to show events using 24h format

Steps to reproduce the issue

Set profile language to English
Set profile time Format to 24 hours
Enable the calendar view (I used google calendar)

What version of Home Assistant Core has the issue?

core-2021.8.8

What was the last working version of Home Assistant Core?

No response

In which browser are you experiencing the issue with?

Microsoft Edge Version 92.0.902.78

Which operating system are you using to run this browser?

Windows 10 21H1

State of relevant entities

No response

Problem-relevant frontend configuration

Profile Language = English
Profile Time format =  24 hours

Javascript errors shown in your browser console/inspector

No response

Additional information

It seems to be caused by only telling fullcalendar the locale (en)
locale.eventTimeFormat can (and probably should) be specified explicitly https://fullcalendar.io/docs/locale