Universal and Local Time
Coordinated Universal Time (UTC) is a world time that is not
affected by any time zone or seasonal time changes, and is defined
by a network of Atomic Clocks. Historically, but incorrectly,
it is often compared to Greenwich Mean Time (GMT), which is an
Astronomical time (related to Earth rotation).
UTC has many applications whenever a uniform, accurate world time
system is required, such as Astronomical events. UTC is also the
basis for all Local (Civil) time systems in the world.
Occasionally (usually 1 January or 1 July) UTC is corrected with a
leap second, to keep it within a tolerance from Astronomical time,
compensating for the slowing down of Earth rotation and other
Find more information on UTC here
To get current UTC on your screen click here
The world is divided in time zones in which local (or civil) time
is offset by a fixed amount from UTC. Most often this offset is an
integer number of hours, although some countries have other
offsets. However the UTC seconds are the same everywhere.
Find a map of world time zones here
Daylight Saving Time
Daylight saving time (DST), (aka Summer time), is the convention of
advancing clocks so that afternoons have more daylight and mornings
Typically clocks are adjusted forward one hour near the start of
spring and are adjusted backward in autumn. The dates that this
happens vary by location and change occasionally. In 2007 both the
USA and New Zealand have changed their definition of DST.
Find more on DST here
New Zealand Standard Time (NZST) is defined as UTC + 12
During the southern summer, New Zealand has Daylight Saving Time
(NZDST) which is defined as UTC + 13 hours.
NZDST starts on the last Sunday in September at 2 am when the
clocks are set to 3 am.
NZDST ends on the first Sunday in April at 3 am when the clocks are
set to 2 am.
If you want to know more about UTC and other time
systems, sign up for our next Astronomy I course.
email a friend