[Observation] Non-uniform rate along ecliptic (uneven seasons) [Modeling mechanism] Eccentric orbit (sun's deferent center off Earth) [Object(s)] 
Sun
S t a r s
S u n
M o o n
T h e 5 p l a n e t s
P l a n e t s
I n t e r i o r p l a n e t s
E x t e r i o r p l a n e t s