When “10 a.m. meeting” means 3 a.m. for someone

On a global team, “let’s meet tomorrow at 10 a.m.” is incomplete unless you say whose 10 a.m. Without time zones, people miss meetings or join at brutal hours.

Basics First

What is UTC?

UTC (Coordinated Universal Time) is the reference for all zones. Local time is UTC plus or minus an offset.

Korea (KST): UTC+9

UK (GMT): UTC+0

US Eastern (EST): UTC-5

US Pacific (PST): UTC-8

When it’s 6 p.m. in Korea (UTC+9), it’s 9 a.m. the same moment in the UK (UTC+0).

The daylight saving trap

Many countries shift clocks forward an hour in summer (DST). Offsets are not fixed all year.

Korea has no DST (UTC+9 year-round)

US and Europe shrink the gap by one hour during part of the year

So “Korea and New York are 14 hours apart” can become 13 hours depending on the season. Transition weeks are especially messy.

Scheduling Across Time Zones

Find golden hours

Map the overlap when everyone is in normal working hours.

Korea + India: relatively generous overlap (3.5-hour difference)

Korea + Europe: Korea afternoon / Europe morning is often the only window

Korea + US: little overlap; one side usually sacrifices

Share the pain fairly

When offsets are large, someone meets at an awkward hour. Rotate so the same region isn’t always on late calls. This week Asia stays late; next week US joins early — that keeps things equitable.

Default to async

With eight or more hours between regions, cut live meetings. Reserve sync time for decisions that truly need it; use docs and recorded updates for the rest.

Practical Tips to Reduce Confusion

Always label the zone: “10 a.m. KST” or “10 a.m. PT”, not bare “10 a.m.”

Use UTC for big cross-region events: One reference time reduces mistakes

Show both local times: “6 p.m. KST / 4 a.m. EST” is considerate

Let tools convert: Having each person mark availability in their own zone and letting the system find overlap is safest

Common Mistakes

1Forgetting DST: Using the usual offset and being off by an hour during transitions

2Ignoring the date line: 9 a.m. in Korea can be the previous evening in the US

3Mixing abbreviations: EST vs EDT, PST vs PDT — easy one-hour errors

Summary

Time zones are one of the most common traps in global work. Label zones, remember DST, and rotate inconvenient slots. Tools that accept local availability and compute overlap remove most manual math — and most of the stress.

Time Zones for Global Teams: A Practical Guide