Diurnal means 'of the quality of the day'
Nocturnal means 'of the quality of the night'
Diurnal energies relate to masculinity and the solar principle, being active, direct and expressive, whilst nocturnal energies relate to femininity and the lunar principle, being responsive, indirect, and impressive. Yin and Yang are analogous oriental terms.
The 'diurnal hemisphere' includes the 7th, 8th, 9th, 10th, 11th, and 12th houses, where planets can be seen above the horizon. The 'nocturnal hemisphere' includes the 1st, 2nd, 3rd, 4th, 5th and 6th houses, where the planets are beneath the horizon and unable to be seen.
A 'diurnal chart' is one where the Sun is located in the diurnal hemisphere - being above the horizon it denotes someone born in the day time and therefore belonging to the diurnal sect. A 'nocturnal chart' is one where the Sun is located in the nocturnal hemisphere - being beneath the horizon it denotes someone born at night and therefore belonging to the nocturnal sect. Many techniques such as firdar require knowledge of the diurnal/nocturnal sect and alternate principle rulership to the Sun or Moon accordingly.
Diurnal revolution is the apparent daily passage of a planet or celestial body by which it rises over the ascendant in the east, towards the midheaven where it culminates (and then on through the descendant and IC back up to the ascendant).
The characteristics of diurnal and nocturnal influences infiltrate all areas of astrological philosophy, from the alternation of the signs (usually referred to as masculine and feminine), to the assignation of planetary rulerships over the signs. Apart from the Sun and Moon each planet has two rulerships - one diurnal, one nocturnal - to recognise their expression in these altered states. For further details on these assignations and how they are expressed see: Traditional Sign Rulerships by Deborah Houlding.
Also see Sect