Science / Tides and Currents / Astronomical Time: Time formerly used in astronomical calculations in which the day began at noon rather than midnight. The astronomical day commenced at noon of the civil day of the same date. The hours of the day were numbered consecutively from zero (noon) to 23 (11 a.m. Of the following morning). Up to the close of the year 1924, astronomical time was in general use in nautical almanacs. Beginning with the year 1925, the American Ephemeris and Nautical Almanac and similar publications of other countries abandoned the old astronomical time and adopted Greenwich civil (mean) time for the data given in their tables.
Science / Tides and Currents / Time: Time is measured by the rotation of the Earth with respect to some point in the celestial sphere and may be designated as sidereal, solar, or lunar, according to whether the measurement is taken in re MORE
Science / Tides and Currents / Civil Time: Time in which the day begins at midnight as distinguished from the former astronomical time in which the day began at noon. MORE