San Francisco is typically 17 hours behind Seoul. When it's 1:00 AM in Seoul, it's 8:00 AM the previous day in San Francisco. South Korea does not observe daylight saving time, but San Francisco 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 SF time (7:00 PM - 9:00 PM Seoul, or 8:00 PM - 10:00 PM in winter). Very early morning SF catches evening Seoul.
San Francisco's tech industry has strong ties to Korean tech giants like Samsung and LG. Many Korean startups have offices in Silicon Valley, and there's a significant Korean-American community in the Bay Area.