Time Difference Between San Francisco and Sydney

Count this pair backwards. Sydney's morning is San Francisco's previous afternoon, and the larger gap is the one that gives California an earlier slot. While San Francisco is on standard time and Sydney is on daylight time, from the first Sunday of November until the second Sunday of March, Sydney is 19 hours ahead, so 9 AM in Sydney is 2 PM the day before in San Francisco. Through the long middle, from the first Sunday of April until the first Sunday of October, the gap is 17 hours and that same 9 AM Sydney call is 4 PM in San Francisco. People who memorize 'about 18 hours' book the wrong afternoon for half the year.

Two shorter bridges sit between those settings, both at 18 hours. One runs from the second Sunday of March until the first Sunday of April, after California has sprung forward and before Sydney has fallen back. The other runs from the first Sunday of October until the first Sunday of November, after Sydney has sprung forward and before California has fallen back. Eighteen hours puts 9 AM Sydney at 3 PM the previous day in San Francisco. The date is the part that gets dropped. A Tuesday morning stand-up in Sydney is still Monday in California, and a recap that says 'tomorrow' without a date lands on the wrong day about half the time.

Nonstop flights run about fifteen hours. Westbound you cross the date line and lose a day: leave San Francisco on Monday evening and you are into Sydney on Wednesday morning. The return hands the day back. A shift of 17 to 19 hours does not reward clever sleep timing. Give the far end two clear days, and do not put Sydney's January in the plan as a normal work month. A lot of Australian leave sits between Christmas and mid-January, which is when San Francisco is back at full speed.