Day 1 = Light

Ok, I'm not religious but I was set this challenge in a group I'm a member of.

THE 7 DAYS OF CREATION (according to Genesis :-))

these are as follows:

Day 1: light
Day 2: Water
Day 3: Ground/Earth/Dry-ness
Day 4: Sky/ Time/ Moon/ Stars/ Sun
Day 5: Birds & Sea Creatures
Day 6: Land Animals (inc. Men & Women)
Day 7: Sabbath/ Holy/ Rest

So day 1 = light!

Can you guess where from??