Best time to call
Seoul is 1 hour ahead of Shanghai. Here are the call windows that respect both your day in Shanghai (China) and theirs in Seoul (South Korea), plus the daylight saving and holiday traps to watch.
9 AM Shanghai
= 10 AM Seoul
9 AM in Shanghai = 10 AM in Seoul, fresh in their morning before the day fills up.
10 AM Shanghai
= 11 AM Seoul
10 AM in Shanghai = 11 AM in Seoul, fresh in their morning before the day fills up.
11 AM Shanghai
= 12 PM Seoul
11 AM in Shanghai = 12 PM in Seoul, right around their lunch, so confirm they are at a desk.
Both cities are loaded with Shanghai 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 is 1 hour ahead of Shanghai. From your desk in Shanghai, that means your morning is already their afternoon, and the window where both teams are at their desks is narrower than it looks. The cleanest single slot is 9 AM your time, which lands at 10 AM in Seoul.
At 1 hour 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: Shanghai 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 China and South Korea are likely off, so do not schedule.