New York is typically 14 hours behind Seoul. When it's 3:00 PM in Seoul, it's 1:00 AM in New York. South Korea does not observe daylight saving time, while New York does.
During US daylight saving time (mid-March to early November), the difference is 13 hours. During US standard time (November to March), it's 14 hours.
Optimal meeting window: 7:00 PM - 10:00 PM New York time (9:00 AM - 12:00 PM Seoul next day). This catches morning business hours in Seoul.
For evening calls to Seoul, schedule 6:00 AM - 8:00 AM New York time (8:00 PM - 10:00 PM Seoul same day).