San Francisco is typically 16 hours behind Singapore. When it's 3:00 PM in Singapore, it's 11:00 PM the previous day in San Francisco. Singapore does not observe daylight saving time, while California does.
During US daylight saving time (mid-March to early November), the difference is 15 hours. During US standard time (November to March), it's 16 hours.
Optimal meeting window: 5:00 PM - 8:00 PM San Francisco time (9:00 AM - 12:00 PM Singapore next day). This catches morning business hours in Singapore.
Tech companies often schedule APAC calls at 6:00 PM Pacific to catch 10:00 AM Singapore.