A day has 24 hours.

In the intense heat, he continued to practice while drenched in sweat.

We went to the pool to beat the heat.

In the midday heat of summer, he continued to work while drenched in sweat.

Do you understand the necessity of this project?

That information is unnecessary.

That information is completely unnecessary.

He thinks that war is a necessary evil.

When the sun rises, a new day begins.

I am busy with work during the daytime.