The Earth's terminator rewpresents a fixed reference to the Sun and
can be demarcated by the direction of the arrows over the course of an
annual orbit -

http://www.honeysucklecreek.net/imag...1-44-6689creth...

http://www.mhhe.com/physsci/astronom...ages/04f15.jpg


The global unequal lengths of the natural noon cycles,supposing axial
rotation is constant or near enough constant, represents a
longitudinal change in the motion of the Earth,this can be
observationally confirmed using the sequence of images from Uranus -

http://astro.berkeley.edu/~imke/Infr..._2001_2005.jpg

With axial rotational orientation at almost 90 degrees to the change
in orbital orientation,it is fairly easy to isolate the orbital
component in Uranus however as axial orientation and rotation runs
almost parallel to the orbital change on Earth it is very difficult to
discern save the unequal lengths of the natural noon cycles.


In the representation demonstrating Keplerian orbital geometry,it is
possible to gauge the longitudinal orbital orientational change
against the fixed orientation of the Earth's terminator at the
Equator,it is also enjoyable to realise that the daylight/darkness
cycles are a consequence of the slow and majestic change in the
Earth's orbital orientation.


There is no advantage in maintaining 'axial tilt' as a pseudo-
dynamic,the fact that local rotations and orientations can blot out
larger motions is probably the main reason why the false perception
still remains -

http://www.astronomy.org/programs/se...asons-for-seas

It is the Equinox and while all life along a given meridian share the
same length of a natural day or natural noon cycle ,for only two days
a year all life along a given meridian share the same length of
daylight/darkness..