How can the sun be created after day and night? "Light" was created on day 1 - Genesis 1:3-5.  However the sun was created on day 4 - Genesis 1:14-19.

How is this possible?
Let's look more closely at your linked verses:


  5 God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day. (Genesis 1:5)


This verse implies the creation of light and the implementation of it to create the first day. Darkness already existed, so only light was needed.


  16 God made two great lights&mdash;the greater light to govern the day and the lesser light to govern the night.


This verse implies the creation of the sun and moon&mdash;notice the "greater" and "lesser" lights.

These lights&mdash;the sun and the moon, which were created three days after light itself was&mdash;are simply vessels to carry greater and lesser versions of the previously created light which govern the limits of the day and of the night.

And if we read a bit further:


  16 cont. He also made the stars. 17 God set them in the vault of the sky to give light on the earth, 18 to govern the day and the night, and to separate light from darkness. And God saw that it was good.


Stars were created to be vessels for light as well, but to separate this greater light (the sun) from this lesser light (the moon), and to govern both day and night.

Before questioning the bible (and God, by extension), always look more closely at what is being said and you will understand. This is especially true for scripture, because many times we find it to be ambiguous, but upon closer examination it just comes to us.