Seattle is typically 17 hours behind Seoul. When it's 1:00 AM in Seoul, it's 8:00 AM the previous day in Seattle. South Korea does not observe daylight saving time, but Seattle does.
During US daylight saving time (March to November), the difference is 16 hours. During US standard time (November to March), the difference increases to 17 hours.
Optimal meeting window: 3:00 AM - 5:00 AM Seattle time (7:00 PM - 9:00 PM Seoul, or 8:00 PM - 10:00 PM in winter). Very early morning Seattle catches evening Seoul.
Seattle has direct flights to Seoul and a large Korean-American community. Boeing has significant business relationships with Korean Air and other Korean aviation companies.