In the graph below you see the time zone difference between Greenwich Mean Time and Pacific Standard Time. Drag the bubble to adjust the time and to see the corresponding time in the other time zone.
Greenwich Mean Time is the time zone of the 0 meridian, located in London, United Kingdom, including cities like London, Lisbon and Dublin (in the winter). Pacific Standard Time is the time zone of the Canadian and US West Coast, with places like Seattle, Vancouver, San Francisco and Los Angeles.
Usually it is preferable to schedule meetings in the late afternoon for the person in GMT and before lunch for the person in PST.
GMT, or Greenwich Mean Time, is the zero when it comes to time zones – they are all counted from the zero meridian that runs through the village of Greenwich.
While both the UK and Portugal are officially on GMT you need to pay attention to whether they are actually observing it or are using their own. Britain in the summer for example use British Summer Time – which is different than GMT.
London, Lisbon, Dublin, Edinburgh
GMT does not observe DST as it is the zero hour time zone – it never changes.
Pacific Standard Time is the time of the Western United States and Canada and is typically abbreviated as PST. It is 8 hours behind GMT. This means that when the clock is noon in London (GMT), it is 4AM in Seattle (PST).
Most of the Western US and Canada are following Pacific Standard Time.
This can be a bit tricky as most states on the US Pacific Coast do apply daylight saving time, calling PST for PDT, or Pacific Daylight Time, instead and sets the clocks in November and March respectively.