UTC is the stable reference
UTC is commonly used as a global time reference in software, aviation, logs, and international coordination.
An offset such as UTC+08:00 tells you the difference from UTC at that moment, but it does not describe daylight saving rules by itself.
City zones include rule history
A city-based zone such as America/New_York includes daylight saving transitions and historical changes. That makes it better for future calendar events.
For a recurring meeting, choose a city zone rather than a fixed offset when participants expect local daylight saving changes to apply.
GMT in everyday use
GMT is often used casually as a reference similar to UTC, but technical systems normally prefer UTC.
When precision matters, write the exact offset or city zone instead of relying on a vague abbreviation.