US Premarket and After-Hours in UK Time

US premarket and after-hours in UK time run from 9:00am to 1:00am the next morning for most of the year. The US extended trading day opens at 4:00am ET, five and a half hours before the main session, and the last after-hours prints land at 8:00pm ET. New York sits five hours behind the UK clock for all but about four weeks of the year, which puts a complete US trading day between mid-morning and just after midnight in London. Our US stock market hours in London time guide covers the 9:30am to 4:00pm ET regular session only. This page adds the hours either side of it.

US premarket and after-hours in UK time, hour by hour

The panel below takes every one-minute bar in SPY, the largest S&P 500 tracker fund, across September 2026 and groups it by the hour of the New York clock it fell in, with the matching London hour alongside. It is the extended day as a UK account meets it, with the traded volume of each hour attached rather than a bare schedule.

WITH bars AS
(
    SELECT
        toTimeZone(window_start, 'America/New_York') AS et,
        toTimeZone(window_start, 'Europe/London')    AS uk,
        volume
    FROM global_markets.delayed_stocks_minute_aggs
    WHERE ticker = 'SPY'
      AND window_start >= '2026-09-01 00:00:00'
      AND window_start <  '2026-10-01 00:00:00'
      AND toHour(toTimeZone(window_start, 'America/New_York')) BETWEEN 4 AND 19
)
SELECT
    formatDateTime(toStartOfHour(et), '%H:%i')                                     AS et_time,
    formatDateTime(toStartOfHour(uk), '%H:%i')                                     AS london_time,
    round(sum(volume) / countDistinct(toDate(et)) / 1000, 1)                       AS avg_session_volume_k,
    round(100 * sum(volume) / (SELECT sum(volume) FROM bars), 2)                   AS share_of_day_pct
FROM bars
GROUP BY et_time, london_time
ORDER BY et_time

Read the London column top to bottom and the shape of the day appears. The premarket's first hour opens at 09:00 UK time, and the final extended-hours hour begins at 00:00 and runs to 1:00am. The volume column is the part a schedule cannot tell you: that opening premarket hour carried 0.56% of SPY's full-day shares, against 11.36% in the 14:00 UK hour that contains the New York open, which averaged 4831.6 thousand shares per session. The last hour of the after-hours block, the one that ends at 1:00am UK, took 0.09%.

The four reference points of the extended day, in UK clock time while both countries keep summer time:

• 9:00am UK: the US premarket session opens (4:00am ET)
• 2:30pm UK: the regular session opens (9:30am ET)
• 9:00pm UK: the regular session closes, and the closing auction prints (4:00pm ET)
• 1:00am UK: after-hours trading ends (8:00pm ET)

A deeper walk through what each block is for, in ET, sits in after-hours and premarket trading.

Do BST and GMT change US market hours in UK time?

For most of the year, no. Britain keeps British Summer Time from late March to late October; the United States keeps Eastern Daylight Time over an overlapping stretch. While both are on their summer clock the gap is five hours, and while both are on their winter clock it is also five hours. The UK times listed above hold in BST and in GMT alike: the US open is 2:30pm UK in July and 2:30pm UK in January, and the premarket opens at 9:00am either way.

What moves is the handful of sessions where the two countries are out of step. The UK changes on the last Sunday of October and the last Sunday of March. The United States changes on the first Sunday of November and the second Sunday of March. Those dates do not line up, which leaves one week each autumn and three weeks each spring at a four-hour gap. The mechanics of the US side are set out in US market hours and daylight saving.

The autumn week when the gap is four hours

In 2026 the UK puts its clocks back on Sunday 25 October. The United States follows a week later, on Sunday 1 November. The five US sessions in between, Monday 26 October through Friday 30 October 2026, land one hour earlier on a UK clock than usual:

• 8:00am UK: the US premarket session opens
• 1:30pm UK: the regular session opens
• 8:00pm UK: the regular session closes
• midnight UK: after-hours trading ends

This is not a quirk of 2026. The same mismatch opened in 2025, when the UK changed on 26 October and the United States on 2 November, and it is visible directly in the tape. The panel below finds the 9:30am ET bar of each SPY session across late October 2025 and prints the London clock time of that exact minute.

SELECT
    toString(toDate(toTimeZone(window_start, 'America/New_York')))                       AS session_date,
    any(formatDateTime(toTimeZone(window_start, 'America/New_York'), '%a %e %b'))        AS session_label,
    formatDateTime(any(toTimeZone(window_start, 'Europe/London')), '%H:%i')              AS london_clock_at_us_open,
    toUInt8((toHour(any(toTimeZone(window_start, 'Europe/London')))
             - toHour(any(toTimeZone(window_start, 'America/New_York'))) + 24) % 24)     AS hours_ahead_of_new_york
FROM global_markets.delayed_stocks_minute_aggs
WHERE ticker = 'SPY'
  AND window_start >= '2025-10-17 00:00:00'
  AND window_start <  '2025-11-08 00:00:00'
  AND (toHour(toTimeZone(window_start, 'America/New_York')) * 60
       + toMinute(toTimeZone(window_start, 'America/New_York'))) = 570
GROUP BY session_date
ORDER BY session_date

The line chart steps down and back up. Across the 16 sessions in view, the opening minute printed at 14:30 London time at the start of the window, 5 hours ahead of New York. On Mon 27 Oct the same minute printed at 13:30, a gap of 4 hours, and it stayed there until the US clocks changed. By the last session in the window the gap was back to 5 hours and the open was back at 14:30 London time.

The spring version runs longer. In 2026 the United States moved to summer time on 8 March while the UK waited until 29 March, leaving three weeks at four hours. A calendar alert set to "2:30pm, US open" is wrong for about twenty sessions a year.

What trades in the UK morning and the UK evening

Extended-hours sessions are electronic order books with no auction attached. There is no opening or closing cross outside the regular session, and premarket and after-hours orders rest on alternative trading systems rather than printing through the primary exchange's auction. Two things decide what a UK-based account can reach: whether the broker passes orders to a venue in that window at all (many offer part of the block rather than all sixteen hours), and how wide the book is when the order arrives.

Width is measurable. The panel below takes every quote update in AAPL across one full extended day, Tuesday 15 September 2026, and reports the median quoted spread in basis points for each hour, where one basis point is one hundredth of a percent of the share price.

WITH q AS
(
    SELECT
        toTimeZone(sip_timestamp, 'America/New_York') AS et,
        toTimeZone(sip_timestamp, 'Europe/London')    AS uk,
        toUInt64(sequence_number)                     AS seq,
        10000 * (toFloat64(ask_price) - toFloat64(bid_price))
              / ((toFloat64(ask_price) + toFloat64(bid_price)) / 2) AS spread_bps
    FROM global_markets.cache_stocks_quotes
    WHERE ticker = 'AAPL'
      AND sip_timestamp >= '2026-09-15 08:00:00'
      AND sip_timestamp <  '2026-09-16 00:00:00'
      AND bid_price > 0
      AND ask_price >= bid_price
)
SELECT
    formatDateTime(toStartOfHour(et), '%H:%i')          AS et_time,
    formatDateTime(toStartOfHour(uk), '%H:%i')          AS london_time,
    round(quantileDeterministic(0.5)(spread_bps, seq), 2) AS median_spread_bps
    ,
    count()                                             AS quote_update_count
FROM q
GROUP BY et_time, london_time
ORDER BY et_time

The spread line sags in the middle of the day and lifts at both ends. In the 04:00 ET hour, 09:00 in London, the median spread measured 6.96 basis points on 1528 quote updates. In the 10:00 ET hour, mid-session, it measured 1.21 basis points on 135693 updates. The final hour of the extended day, ending at 1:00am UK, came in at 3.01 basis points. That is the cost of the early UK morning and the late UK night stated as a number: the same stock, the same day, a wider quote and a fraction of the quote traffic.

Why extended-hours orders have to be limit orders

A market order asks for the best price available right now. In a book that quotes a few hundred shares a side, "available right now" can sit far from the last print, and the fill arrives before the trader sees it. Brokers that offer premarket, after-hours and overnight access generally accept limit orders only in those windows, which caps the price at the figure you name and leaves the order unfilled when nothing reaches it. The reasoning is set out in full in why overnight orders must be limit orders, and the order-type mechanics live in overnight trading order types.

One further point for a UK reader: the sixteen-hour day described above is no longer the outer boundary. Venues have extended toward a near-continuous weekday schedule, which moves the US tape into the UK afternoon of the previous day. That change, and what it does to a London clock, is covered in can you trade US stocks 24 hours.

FAQ

What time is the US premarket in UK time?

The US premarket session opens at 4:00am ET, which is 9:00am in the UK while both countries are on their summer clock and also 9:00am while both are on their winter clock. It runs until the regular session opens at 2:30pm UK time.

Are US market hours in UK time different in BST and GMT?

For most of the year they are identical, since the UK and the United States both add an hour in summer. The US open is 2:30pm UK in BST and 2:30pm UK in GMT. The exception is the few weeks when the two countries have not yet changed together.

When is the UK to New York gap four hours in 2026?

Britain puts its clocks back on Sunday 25 October 2026 and the United States on Sunday 1 November 2026, so the sessions of Monday 26 October through Friday 30 October 2026 run at a four-hour gap. The US open falls at 1:30pm UK time on those five days. The spring mismatch covered 9 March to 27 March 2026.

How late can a UK account trade US stocks?

Regular after-hours trading ends at 8:00pm ET, which is 1:00am in the UK, or midnight during the autumn mismatch week. Access to the full window varies by account, and extended-hours orders are typically restricted to limit orders.

Every panel on this page carries the exact SQL beneath it, open one to see how the hours were counted. To check the London clock time of any US session, or how wide a book was at a given hour, ask the question in plain English on the Strasmore terminal.