Change in Venus Express's local time at ascending node
The Local Time at Ascending Node (LTAN) is the local time at which the spacecraft passes the Venusian equator on the ascending branch. For the first orbit (2144, on 4 March 2012), the LTAN is 23:47, for the last orbit (2171, on 31 March 2012), it is 02:42.
As on Earth, standard time zones are defined by geometrically subdividing Venus' spheroid into 24 wedge-shaped sections bordered by meridians, each 15° longitude apart. The local time in neighboring zones would differ by one Venus hour, or 1/24th of a Venus day. The variation in the position of the Sun from one end of the zone to the other (East vs. West) would be 1/24th of the sky.