The week UK clocks change before US clocks and US data lands at 12:30 London

[Fairman]

The week UK clocks change before US clocks and US data lands at 12:30 London

This coming week is one of the two odd weeks of the year. The UK leaves summer time on the last Sunday of October, which is 25 October this year. The US doesn't change until the first Sunday of November, 1 November. For those six or seven days the gap between London and New York is four hours instead of the usual five.

The practical effect: anything released at 8:30 in New York prints at 12:30 London, not 13:30. Anything at 10:00 New York lands at 14:00. The US equity open at 9:30 New York is 13:30 London.

If your platform calendar is set to your local time and pulls times properly, it should show the right hour. If you work from a mental schedule, or a notes file that says US data is at 13:30, you can be caught flat-footed. The same thing happens in March, when the US changes first and the gap shrinks to four hours for a few weeks.

The other effect is on the overlap. London and New York share an extra hour of trading in the afternoon, so the busy period starts an hour earlier in London terms. On EURUSD and GBPUSD that usually means the lunchtime lull is shorter than normal.

For this week I've moved every US release on my calendar by hand and set alerts 10 minutes before each one. Easy to do, easy to forget.

[FXS HongKong Scalper]

Useful heads up, and from Hong Kong the week looks different again since we never change clocks. This week US data at 8:30 New York prints at 20:30 HK, and from 2 November it moves to 21:30. The London open meanwhile already shifted to 16:00 HK today. So for one week the gap between the London open and the US numbers is four and a half hours instead of five and a half. Anyone running session filters keyed to HK time needs two separate edits, one this week and one next.

[Fairman]

Broker server time is the other half of this. Many brokers keep their servers on GMT+2 in winter and GMT+3 in summer, switching with the US, so that the daily candle closes at 17:00 New York. During the gap week, the server is still on GMT+3 while London has gone back to GMT. So London 08:00 shows as 11:00 on the server, instead of the usual 10:00. If you have session boxes or time filters set in server time, they're an hour off until 1 November. Some brokers do switch with the UK instead, so check yours rather than assuming.

[Fairman]

Asian sessions are affected too, but less. Tokyo doesn't use daylight saving, so Tokyo opens at 00:00 London once the UK is back on GMT, compared with 01:00 during summer. Sydney moved to daylight saving at the start of October, so its relationship with London has changed twice in a month. If you trade the Asian range and mark it in London time, check that your box still starts and ends at the hours you mean, because it may have quietly shifted. New Zealand also moved to summer time in late September, so NZD traders get the same shuffle.

[Fairman]

One thing I'd watch for is thinner liquidity at the start of the US release on these weeks. Some US traders and desks are at their desks at the usual local time, so nothing changes for them, but European participants who plan around a fixed London time can be late. I don't have hard data on whether the first minute is wilder on gap weeks, but it's an easy thing to log. If anyone has a few years of tick data, comparing 12:30 prints to normal 13:30 prints would make an interesting test.

[Fairman]

For scheduled central bank events the same rule holds. The FOMC statement comes out at 14:00 New York, which is normally 19:00 London but 18:00 in a gap week if a meeting falls in one. That's a big change for anyone in Europe planning to be at the screen for the press conference half an hour later. Most of the time FOMC dates don't land in these weeks, but it's a quick check whenever the calendar is published. For anyone using a printed weekly plan, a note at the top saying US times minus one hour is a simple fix.

[Shadow Trader]

Thanksgiving, July 4th, Memorial Day. The US is closed, but spot FX still trades. London is working, Asia has already finished its day, and the afternoon session that normally brings New York volume just doesn't arrive.

Picture a scalper sitting down at 1pm New York time on a holiday, expecting the usual afternoon action. The feed shows a bit of movement and the spread is a touch wider. A setup appears and looks identical to dozens that worked before. The trade goes in, and nothing follows through. Price drifts, ticks sideways, and then jerks against the position on a single thin print.

What changed isn't the pattern. It's the participants. No US banks, no US funds, far fewer algorithms running at full size.

Settlement matters too. Dollar value dates on a US holiday shift, and rollover pricing can get odd around them.

Checking a bank holiday calendar for the main currencies takes a minute and prevents a lot of confusing sessions.

Does the same strategy behave differently on US holidays, or is it just a matter of lower volatility?