Time zones are more than a number
Why a named time zone is safer than a fixed UTC offset when planning ahead.
An offset describes one moment
A UTC offset tells you how far a local clock is from UTC at a particular instant. It does not necessarily tell you what the offset will be next month.
A named IANA time zone, such as America/New_York, identifies a set of historical and current time rules. The date and zone together determine the offset.
Always bring the date
When scheduling a call, “10 AM in New York” is incomplete without a date. Regions can change their clocks on different weekends, and some do not change clocks at all.
Convert the complete local date and time to each destination. Check the destination date too: crossing time zones can move a meeting into the next or previous day.
Rules can change
Governments decide time-zone rules. Browsers and operating systems need current time-zone data to reflect changes. Keep your software updated, especially when arranging future events in regions with recent rule changes.