Day and night are caused by the Earth's rotation on its axis over 24 hours. Weeks consist of 7 days which are associated with the sun and visible objects in the night sky. Months are based on the moon's approximately 29.5 day revolution around Earth, though months contain 30-31 days. Years measure the 365.2422 days it takes Earth to orbit the sun, requiring a leap year every four years, except for centennial years which must be divisible by 400 to be a leap year.

2. Day and Night
 Caused by the spin of the Earth on its axis
 Takes about 24 hours for the Earth to make
one rotation

3. Weeks
 7 days for the…
 7 non star visible objects in the sky
 Although not all connections are obvious in
English!
Day Object
Sunday Sun
Monday Moon
Tuesday Mars
Wednesday Mercury
Thursday Jupiter
Friday Venus
Saturday Saturn

4. Months
 Month sounds like moon!
 Even though the moon takes about 29.5 days
to revolve around the Earth and our months
are usually 30-31 days, we based months off
of the moon!

5. Years
 Years are based on how long it takes the
Earth to make one complete orbit around the
sun
 It takes the Earth 365.2422 days to orbit the
sun
 Because of that, we have leap year every four
years
 On years that end in a 00, it must also be
divisible by 400 to be a leap year (1900 was
not a leap year but 2000 was).

6. Years
 Years are based on how long it takes the
Earth to make one complete orbit around the
sun
 It takes the Earth 365.2422 days to orbit the
sun
 Because of that, we have leap year every four
years
 On years that end in a 00, it must also be
divisible by 400 to be a leap year (1900 was
not a leap year but 2000 was).