Local
solar time or
sundial time was used until the early 19th century when accurate mechanical clocks became commonplace. Local mean time continued in use until various countries adopted a national
standard time. Each town or city kept its own
meridian, so locations one degree of longitude apart had times four minutes apart. This became a problem in the mid 19th century when railways needed clocks for
railway time that were synchronized between stations, while local people needed to match their clock (or the church clock) to the time tables.
Standard time means that the same
time is used throughout some regional time zone—usually, it is at an offset from
Greenwich Mean Time or the local mean time of the
capital of the region. ==See also==