Deep Mothering Question #1

I do not understand this phenomenon:

Week nights - children extremely difficult to get into bed. Energy abounds and talking won't stop.

Week days - children extremely difficult to get out of bed. Crankiness abounds and whining won't stop.

Weekend nights - children pass out around 8:30 pm.

Weekend mornings - children wake up at 6:30 am in chipper moods and want to spend quality time with groggy parents.

Why?