London is five hours ahead of New York City at most times of the year. In other words, when it's 3 pm in New York (or noon in Los Angeles), it's 8 pm in London. Note that Great Britain and most European countries also move their clocks ahead for the one-hour differential when daylight saving time goes into effect (although they make the changeover several weeks after the United States).
Timeanddate.com. This site can help you figure out the time anywhere in the world. www.timeanddate.com/worldclock.