[DOC] [TLE] Clock - Wikipedia [PAR] A clock is an instrument to indicate, keep, and co-ordinate time. The word clock is 
derived .... Sundials continued to be used to monitor the performance of clocks 
until the .... These mechanical clocks were intended for two main purposes: for .... 
Some of the more basic table clocks have only one time-keeping hand, with the... [DOC] [TLE] History of timekeeping devices - Wikipedia [PAR] For thousands of years, devices have been used to measure and keep track of 
time. ... Other ancient timekeeping devices include the candle clock, used in 
ancient ... The pendulum clock remained the most accurate timekeeper until the 
1930s, ...... to keep the time of a fixed locationusually Greenwich Mean Time
allowing... [DOC] [TLE] Clock a History - Timekeepers - Timekeepingsite.org [PAR] Mankind has used the sun, water clock, Clepsydras, candle alarm clock, ... 
Historians do not know who or when mankind "invented" a time-keeping device 
or "clock". ... available to use for converting the Sundial time to your local Mean 
Solar time. ... however, it was not until the invention of the pendulum-regulated 
clock after... [DOC] [TLE] The Vortic Watch Company Blog | Horological Stories and ... [PAR] 5 days ago ... (E) Crystal - A watch crystal is the glass on the front or back of the watch ... All of 
Vortic's watches use a mechanical movement to keep time. ... the only way to 
keep time without a clock nearby before quartz watches were invented. .... GMT - 
The name is derived from the term Greenwich Mean Time, created... [DOC] [TLE] Well It&#39;s About Time - SANS Institute [PAR] A brief overview of how a typical Windows environment keeps up .... Stratum 1 
clocks usually synchronize to some national time source by way of ... time in a 
global sense we use the term Greenwich Mean Time (GMT). .... frequency of 
these two fields is tuned until it equals the difference between two ..... Crystal City, 
VAUS. [DOC] [TLE] Clocks change for British Summer Time. But why does the time ... [PAR] Mar 27, 2016 ... Typically, regions with summer time adjust clocks forward one hour close to the ... 
a year before Germany adopted his clock-changing plan on April 30, 1916 when 
... A few European countries don't use DST at all: Russia, Iceland, ... During these 
summers, therefore, Britain was two hours ahead of GMT and... [DOC] [TLE] Tracking Time - The Christ Myth [PAR] Before 2000 BCE, the Babylonians (in today's Iraq) used a year of 12 alternating 
... Our ways of keeping track of the passage of time include the position of clock 
hands and ... preceding these public clocks, which were weight-driven and 
regulated by a .... with a clock which keeps mean solar time (i.e. Greenwich Mean 
Time). [DOC] [TLE] History & info - Standard time began with the railroads - Webexhibits [PAR] Standard Time in the US Standard time in time zones was instituted in the ... were 
used well into the Middle Ages, at which time mechanical clocks began to ... 
Britain was the first country to set the time throughout a region to one standard 
time. ... of public clocks in Britain were set to GMT (though some, like the great 
clock on... [DOC] [TLE] An essay on time - Jodrell Bank Centre for Astrophysics [PAR] one year. This time standard became known as Greenwich Mean Time (GMT). ... 
The use of GMT has the consequence that, during the year, our clocks get in and 
out .... These are rather fun, and until the invention of the pendulum clock, the 
most .... as time standards include a crystal oven to keep the crystal at a constant
... [DOC] [TLE] Before standard time: Distributing time in 19th-century America [PAR] But no one single invention made the distribution of time possible; instead, ... 
Tower clocks--set to local solar mean time with the aid of a sundial and an .... at 
Greenwich during the 1850s (Bache to Airy 1850, Airy 1858, Bennett 1980, 
Howse

Question: Until '39 the clock used to keep Greenwich Mean Time was regulated by one of these crystals
Answer: Quartz