Best time to call
Seoul and Tokyo share the same clock. Here are the call windows that respect both your day in Tokyo (Japan) and theirs in Seoul (South Korea), plus the daylight saving and holiday traps to watch.
10 AM Tokyo
= 10 AM Seoul
10 AM in Tokyo = 10 AM in Seoul, fresh in their morning before the day fills up.
11 AM Tokyo
= 11 AM Seoul
11 AM in Tokyo = 11 AM in Seoul, fresh in their morning before the day fills up.
12 PM Tokyo
= 12 PM Seoul
12 PM in Tokyo = 12 PM in Seoul, right around their lunch, so confirm they are at a desk.
Both cities are loaded with Tokyo as the anchor. Adjust the day or hours to see the overlap shift, including around daylight saving transitions.
Sorted by participants in business hours
Green = inside 9:00–17:00
Seoul and Tokyo sit on the same clock, so calling is as easy as calling next door. Pick any slot inside both teams' working day and it lands the same on each end. The only thing worth checking is whether one side observes daylight saving and the other does not, which would quietly open a one-hour gap for part of the year.
At 0 hours apart, you have a generous shared working day. Most of your morning lines up with most of theirs, so the choice is less about finding any overlap and more about hitting the callee's best energy. Aim for their mid-morning rather than their lunch or their wind-down.
The recommended slots above are computed against today's offset, which is the safe default. The trap is the twice-a-year daylight saving changeover: Tokyo and Seoul do not necessarily move their clocks on the same weekend, so for a few weeks each spring and autumn the gap can shift by an hour and every recurring invite quietly misfires. If your call is near a transition date, confirm the exact wall-clock time on both ends rather than trusting the difference.
On these dates both Japan and South Korea are likely off, so do not schedule.