G
LOSSARY AND
A
BBREVIATIONS
8030HEPTA/GPS GPS - NTP Time Server with 2x 10/100/1000 MBit LAN Interface - V04.00
164 / 178
hopf
Elektronik GmbH
Nottebohmstr. 41
• D-58511 Lüdenscheid • Tel.: +49 (0)2351 9386-86 • Fax: +49 (0)2351 9386-93 • Internet: http://www.hopf.com • E-Mail: [email protected]
14.2.1 Time-Specific Expressions
UTC
UTC Time
(
U
niversal
T
ime
C
oordinated) was depending
on the Greenwich Mean Time (GMT) definition of the zero
meridian. While GMT follows astrological calculations,
UTC is based on the stability and accuracy of the Caesium
standard. The leap second was defined in order to cover
this deviation.
Time Zone
The globe was originally divided into 24 longitudinal seg-
ments or time zones. Today, however, there are a number
of time zones which in part apply specifically to certain in-
dividual countries only.
In relation to the time zones, consideration was given to
the fact that local daylight and sunlight coincide at differ-
ent times in the individual time zones.
The zero meridian runs through the British city of Green-
wich.
Time Offset
This is the difference between UTC and the valid standard
time of the current time zone.
The Time Offset will be commit from the local time zone.
Local Standard Time
(winter time)
Standard Time = UTC + Time Offset
The time offset is defined by the local time zone and the lo-
cal political regulations.
Daylight Saving Time
(summer time)
Offset of Daylight Saving Time = + 1h
Daylight Saving Time was introduced to reduce the energy
requirement in some countries. In this case one hour is
added to the standard time during the summer months.
Local Time
Local Time = Standard Time if exists with summer / winter
time changeover
Leap Second
A leap second is a second which is added to the official
time (UTC) in order to synchronise this with Greenwich
Mean Time when required.
Leap seconds are defined internationally by the
Interna-
tional Earth Rotation and Reference Systems Service
(IERS)
.
