Local mean time (LMT) is a form ofsolar time that corrects the variations oflocal apparent time, forming a uniform time scale at a specificlongitude. This measurement of time was used for everyday use during the 19th century beforetime zones were introduced beginning in the late 19th century; it still has some uses in astronomy and navigation.[1]
The difference between local mean time and local apparent time is theequation of time.
Localsolar time orsundial 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 nationalstandard time. Each town or city kept its ownmeridian, so locations one degree of longitude apart had times four minutes apart.[2] This became a problem in the mid 19th century when railways needed clocks forrailway 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 sametime is used throughout some regional time zone—usually, it is at an offset fromGreenwich Mean Time or the local mean time of thecapital of the region.