This line illustrates why Denver is 7 hours behind the UK timewise. Just like we have an imaginary line through the Prime Meridian in the UK which gives us Greenwich Mean Time, so Denver has its own which goes through Union Station. It shows they’re 105 degrees west of our line.
Every 15 degrees east or west (approximately 1035 miles at the equator – the actual distance varies with how far north or south of the equator you are) marks an hour’s difference in time from the previous imaginary line of latitude we’ve divided the earth into from north to south. These lines were established as reference points for astronomical survey work, so that an accurate picture of the sky could be established. Their role in determining relative time across the world came later.
How come there’s a 7 hour difference now we’re in British Summer Time? That’s because the USA also puts their clocks forward in what’s called Daylight Saving time. The particular time zone in Denver is also called Mountain Time.
The time difference meant I woke up very early each day I was there. Sunrise was at 5.30am and that’s when I’d give up trying to sleep and I’d pad over to the huge picture window to watch the changing light over the city from my perch on the 24th floor of my hotel. I spent a lot of time just looking out of the window. The changing light on the distant mountains and the gold dome of the state Capitol building; the occasional thunderstorm moving across the Plains 50 miles away; the shapes of the clouds; and the moon rising over the city were a delight to watch.