Zulu Time is the world time. It is also known as UT or UTC (Universal Time (Co-ordinated)). All over the planet it is the same time. There are no timezones for UTC. UTC also has no Daylight Saving Time or Summer Time.
UTC is based on GMT (Greenwich Mean Time). Greenwich mean time was based upon the time at the zero degree meridian that crossed through Greenwich, England. GMT was first used by the Royal Navy in the 19th century.