MEAN TIME

Wanganui Chronicle, Volume 72, Issue 91, 17 April 1929, Page 9

MEAN TIME

POST OFFICE GUIDE The New Zealand Post and Telegraph Guido which has recently been issued contains some very interesting information in connection with mean times in various countries. The earth’s axial rotation is the phenomenon by which time is measured everywhere on the earth’s surface. It has long been (he custom to divide the day into 24 hours, or rather into two sets of 12 hours, mean solar time. Twelve o’clock noon, corresponds to the meridian passage of the mean sun; and each day begins at twelve midnight. Passing westward tho instant at which tho sun crosses tho meridian occurs later and later, as measured on a clock keeping Greenwich time. Time is thus, earlier or later, according to its position in relation to Greenwich, in an easterly or westerly direction. Thus, when it is twelve o’clock noon. Greenwich mean time, the hour (local time) at various places on the globe is as follow’s:— Auckland llh. 39m. p.m. Lublin llh. 35m. a.m. Melbourne 9h. 40m. p.m. New York 7h. 4m. a.m. Paris Oh. 9m. p.m. San Francisco 4h. 23m. a.m. Sydney lOh. sm. p.m. From this it may be seen that for every 15 degrees east or west, the necessari alteration in time amounts -o one hour