Why there is no overlap, and the 15 vs 16 hour gap
The math leaves no room. Singapore is UTC+8 all year and does not observe daylight saving. San Francisco is UTC-7 on Pacific Daylight Time (March through early November) and UTC-8 on Pacific Standard Time (November through March). So the gap is 15 hours in summer, 16 hours in winter.
Check it: 9 AM Monday in San Francisco is midnight Tuesday in Singapore. And 9 AM Monday in Singapore is 5 PM Sunday in San Francisco (summer) or 6 PM Sunday (winter). Standard 9-to-6 working hours on both sides share exactly zero minutes. Every meeting is a compromise, and the only honest question is which compromise hurts less.
| San Francisco | Singapore | Verdict |
|---|---|---|
| 5:00 PM (PDT) | 8:00 AM next day | Best: SF end of day, SG start of day |
| 6:00 PM (PDT) | 9:00 AM next day | Good: still inside both comfort zones |
| 7:00 AM (PDT) | 10:00 PM | Tolerable occasionally, harsh for SG |
| 9:00 AM (PDT) | 12:00 AM next day | No: midnight in Singapore |
Times shown for PDT (15-hour gap). After the US falls back to PST in early November, add one hour to the San Francisco side, or equivalently shift the San Francisco time one hour earlier to hold Singapore steady.
The daylight saving wrinkle
Because Singapore never moves, the entire gap shift comes from the US side. When San Francisco falls back to PST in early November, the 5 PM meeting that was landing at 8 AM in Singapore now lands at 9 AM. Teams usually call this a gift, an extra hour of sleep for the Singapore side, but it can break recurring meetings that were stored as fixed San Francisco times with attendees who converted once and forgot. The fix is the same as on every tough pair: store the meeting in both time zones explicitly, and re-confirm the Singapore-side time after the November change.
Rotating the pain fairly
When the only workable window still stretches someone's day, the fair system is rotation, and this is where SF-Singapore teams most often fail. The 5 PM San Francisco slot is mildly inconvenient for nobody: it is the end of one side's day and the start of the other's. But if you need to meet more than twice a week, or across more than these two cities, someone eventually takes the 10 PM slot, and it should never be the same someone every week.
My rule: default everything to async, and when you do need the live window, alternate the direction. Week one at 5 PM SF / 8 AM Singapore; week two at 8 AM SF / 11 PM Singapore, only when unavoidable. The attrition cost of permanently owning someone else's midnight is always higher than the convenience of a fixed calendar slot. For the same playbook on other brutal pairs, see New York to Sydney and US to India.
Check the live overlap for any two cities.
Computed from the real tz database, with automatic daylight saving handling.
Open the Timezone Overlap Planner