Sydney is 17-19 hours ahead of San Francisco depending on daylight saving time. Sydney uses Australian Eastern Time (AEST/AEDT, UTC+10/+11) while San Francisco uses Pacific Time (PT, UTC-8/-7). When it's 12:00 PM in San Francisco, it's typically 7:00 AM the next day in Sydney.
The time difference varies because both cities observe daylight saving time but on opposite schedules (Sydney in Southern Hemisphere summer, San Francisco in Northern Hemisphere summer). This creates complex variations throughout the year.
Best calling time: 7:00 AM - 10:00 AM Sydney time. This corresponds to 2:00 PM - 5:00 PM the previous day in San Francisco, catching late afternoon West Coast business hours.
Sydney and San Francisco are both major Pacific Rim cities with strong tech sectors. Many Australian tech companies have offices in San Francisco, and Silicon Valley firms often establish their Asia-Pacific headquarters in Sydney. The substantial time difference requires careful scheduling.