Issues with macOS Tahoe on MacBook Air

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Feedback - macOS - Apple

FWIW, my calendar starts on Sunday, contacts sync across devices, etc., so some of what you're experiencing may be due to 3rd party apps/extensions you've installed that aren't fully compatible with Tahoe.

See if the problems are present when you boot in safe mode, which disables 3rd party extensions and performs some system cleanup.

Start up your Mac in safe mode - Apple Support

Of course, other things like the rounded corners and button colors are Apple's decisions, though you do get a fair amount of control over the latter in System Settings > Appearance.

Picking up on what my colleague has mentioned " FWIW, my calendar starts on Sunday, contacts sync across devices, etc., so some of what you're experiencing may be due to 3rd party apps/extensions you've installed that aren't fully compatible with Tahoe. "

Part 1 of 2

To Drill Down further and to avoid a session of Q&A, Q&A  and Q&A  

Download the Application Etrecheck  ( External Link ) directly from the Developer.

The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 

This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

Part 2 of 2

There are 4 Categories of Third Party Software / Services that do not belong in macOS.

In no special order 

Third Party 2 Way Firewalls 

like Lulu and Little Snitch 

Commercial VPNs 

They may not be what one believes they are doing for the computer and what they actually are doing behind the scenes They may also reduce you Internet Speeds by upwards of 30% 

https://gist.github.com/joepie91/5a9909939e6ce7d09e29

VPN: What you need to know - Apple Community

Third Party Security Software 

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

The Operating System resides in a Sealed and Read Only Volume that cannot be opened by the User nor by Third Party Applications.

The Only thing this Antivirus software is protecting is the Bank Account of the Developers and for zero return to the User aside from the problems this software creates.

Security. Built right in

Mac app security enhancements

The Built in Security  is all that is required to protect the computer.

Protecting against malware in macOS

Third Party Disk Cleaners / Optimizer 

Any Third Party Applications that will interfere with the normal operation of the OS,  is an invitation for disaster. 

Certain Applications maybe available on the Apple Apps Store - this only means the Developer is prepared to pay Apple a percentage on each sale. 

What the Application may do to the computer is up to the User to check this out before purchase

To put the Third Party Disk Cleaner / Optimizer in context and the damages it may have or has already done.

This type of applications can or will Muck Up your User Account ( Home Folder ) of this machine.

It does not touch the Operating System itself unless you consider your User Account ( Home Folder ) as part of the Operating System.

The Operating System is hosed