USA-UK time zone difference

Of all the long-haul pairings, the United States and the United Kingdom is one of the kindest. The UK is always ahead, so your morning is their afternoon, and there is a genuine block of the working day where everyone is awake at once.

How far ahead is the UK?

The UK is on GMT in winter and BST in summer, and the US shifts its clocks too. For most of the year the offsets below hold steady. They only wobble for the few weeks each spring and autumn when one country has changed its clocks and the other has not.

Worked conversions

Using the steady offsets (UK 5 hours ahead of ET, 8 hours ahead of PT), here is what common US times become in London.

The takeaway: from the East Coast, schedule before lunch and you'll catch London mid-afternoon. From the West Coast the overlap is narrower - your early morning is London's late afternoon, so 8 AM PT (4 PM London) is about the last comfortable slot before the UK clocks off.

The best shared window

For a meeting that suits both sides, aim for US morning against UK afternoon. 9 AM–12 PM ET is 2–5 PM in London, squarely inside everyone's working day. West Coast teams should start as early as they can: 7–8 AM PT is 3–4 PM London, which still lands before the UK day ends.

For a deeper look at one specific pair, see our guide to the London to New York time difference, or the best windows in our guide to calling the UK from the USA.

British summer time is set in law, not by custom

The dates are statutory. The Summer Time Order 2002 defines the period as “beginning at one o'clock, Greenwich mean time, in the morning of the last Sunday in March and ending at one o'clock, Greenwich mean time, in the morning of the last Sunday in October”.

The detail that matters for scheduling is the one o'clock GMT, not the calendar dates. Because the change is pinned to a fixed instant in UTC, the UK and the rest of Europe move at the same moment, which is why the London-to-Berlin gap never changes while the London-to-New York gap moves twice a year. The US shifts on its own dates, and for roughly three weeks in March and one in late October the transatlantic gap is an hour narrower than the rest of the year.

Stop checking this every time

If you work across the Atlantic regularly, doing this arithmetic by hand gets old fast, and the brief daylight-saving mismatch is exactly where mistakes creep in. Atlas keeps London and your own US city side by side in your Mac menu bar, shades the hours when both sides 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 would rather compare tools first, we look at the Mac menu bar time zone apps and the time zone meeting planners.