The short answer: London is 8 hours ahead of San Francisco for most of the year (occasionally 7 during the spring changeover weeks). When it is 9:00 AM in San Francisco it is 5:00 PM in London. The best overlap is your morning: 8:00–10:00 AM in San Francisco is 4:00–6:00 PM in London, the end of the London workday.
San Francisco and London sit on opposite sides of an ocean and a continent, but the gap between them is one of the friendlier transatlantic ones. With eight hours between you, your morning lines up neatly with London's late afternoon, leaving a clean daily window for a call.
How far ahead is London?
San Francisco keeps Pacific Time (PST in winter, PDT in summer). London keeps Greenwich Mean Time in winter and British Summer Time in the warmer months. Both sides change their clocks, but on slightly different dates, which is why the usual eight-hour gap occasionally narrows to seven.
| Period | London is ahead by |
|---|---|
| Most of the year | 8 hours |
| Spring changeover weeks | 7 hours |
For day-to-day planning, treat the difference as eight hours. The seven-hour spell lasts only a couple of weeks each spring, when the US and UK have not yet both moved their clocks forward.
The best window to call
Because London is ahead, your morning is their afternoon. Aim for the end of the London working day, which is comfortably early in San Francisco and still inside business hours in London.
| San Francisco (PT) | London (GMT/BST) |
|---|---|
| 8:00 AM | 4:00 PM |
| 9:00 AM | 5:00 PM |
| 10:00 AM | 6:00 PM |
| 12:00 PM | 8:00 PM |
| 5:00 PM | 1:00 AM (next day) |
The sweet spot is 8:00 to 10:00 AM in San Francisco, which is 4:00 to 6:00 PM in London. Push much past noon your time and you are into London's evening; by 5:00 PM in San Francisco it is already the small hours in London.
For a business call vs a personal call
For a work call, your early-to-mid morning is the only sensible slot: it catches London colleagues before they wrap up for the day. Try to book it before 10:00 AM your time so London is still at their desks rather than commuting home.
For a personal call, you have a little more room. A late-morning call from San Francisco lands in London's early evening, a relaxed after-work hour before dinner.
San Francisco and London both observe daylight saving, but they switch on different dates in spring. For a couple of weeks the usual 8-hour gap drops to 7, so a recurring call can land an hour off until both clocks have moved. See the USA to UK time difference for the full picture.
Stop checking this every time
If you work with London regularly, doing this arithmetic by hand gets old fast, and the spring changeover is exactly where mistakes creep in. Atlas keeps San Francisco and London side by side in your Mac menu bar, shades the hours when both cities are awake, and writes any meeting to your calendar in both local times. One glance tells you whether now is a good time to call. If you are further south, see our Los Angeles to London time difference guide.
Frequently asked
How many hours ahead is London than San Francisco?
What is the best time for a San Francisco to London call?
Why is the gap sometimes 7 hours instead of 8?
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