The Traveling Clock
macOS is designed for mobile professionals. By default, your MacBook relies on Apple’s Location Services to determine exactly where you are in the world. It then uses this geographical data to automatically ping an Apple time server (time.apple.com) and instantly update your system clock and time zone when you step off an airplane in a new city. While generally convenient, this feature can cause massive issues if you use a VPN. If your VPN routes your traffic through Tokyo, macOS might get confused, think you are physically in Japan, and automatically change your clock 14 hours ahead, ruining your calendar alerts and meeting schedules.
Dropping the Anchor
To ensure your calendar remains stable and stop macOS from automatically updating your time zone based on network location data, you must disable the automated time zone setting.
Click the Apple logo in the top-left corner of the screen and select System Settings. In the left-hand navigation sidebar, scroll down and click on General. In the main right-hand panel, click on Date & Time. You will likely see two toggle switches at the top of this menu. The first is “Set time and date automatically” (which keeps your clock accurate to the second; you can usually leave this on). The crucial setting is the second one: Set time zone automatically using your current location. Click this toggle switch to turn it Off. You will be prompted to enter your Mac’s administrator password to confirm. Once disabled, you can manually select your permanent home time zone from the dropdown menu below.