GMT vs PST time zone comparison

How GMT and PST compare

Greenwich Mean Time runs eight hours ahead of Pacific Standard Time during the northern winter, the widest gap most US-UK teams routinely coordinate across. From late March until late October the UK observes British Summer Time (BST, UTC+1) and the US observes Pacific Daylight Time (PDT, UTC-7), so the effective gap shrinks to seven hours. Either way, the overlap window is narrow and unforgiving. The only realistic shared business hour is 5 PM GMT (9 AM PST in winter, 10 AM PDT in summer), which catches the very end of the London day and the very start of the San Francisco day. London is usually winding down by 5 PM, so what you are actually negotiating is a 30-minute call where the London side is browsing for headers to write up before leaving and the West Coast side is making the day's first coffee. For sustained collaboration between London and California — a common posture for VC-backed startups, biotech, and global media — most teams accept that one side will routinely take calls outside their normal hours. The London side takes 6 PM or 7 PM calls; the California side takes 7 AM calls. Recurring weekly meetings on this corridor should rotate, not anchor.

Working-hour overlap

Narrow. Only 5 PM London (9 AM Pacific) sits inside both sides' business day, and London is already on the back end of the afternoon.

When to schedule

The only reliable shared business hour is 5 PM London (9 AM Pacific in winter). Use it for one-off introductions and contract reviews. For ongoing weekly collaboration, alternate between 4 PM London (8 AM Pacific) and 5 PM Pacific (1 AM London) so the burden of inconvenience rotates between the two sides. For asynchronous handoffs, encourage the London side to send the end-of-day write-up before 6 PM London (10 AM Pacific) so the West Coast team has a real morning to act on it before London is back online. Slack channels with both London and Pacific membership should expect a 12-hour quiet window overnight.

Notable context

London-to-California is a defining axis of the modern venture capital and biotech industries. Many US biotech and pharma companies have European HQs in the UK (Astrazeneca, GSK), and US tech firms with London offices (Google, Meta, Amazon) run cross-coast all-hands on this corridor weekly. The standard pattern is a 4 PM or 5 PM London Tuesday all-hands that runs into the late London afternoon, then a Wednesday or Thursday 9 AM Pacific kickoff for the rest of the week. Outside corporate, London-to-Hollywood entertainment deals (book-to-screen rights, music licensing, talent agency) routinely use this corridor and have accepted the inconvenience as normal.