The New American Standard Bible (NASB) on the six days of creation.

And there was evening and there was morning, one day. Genesis 1.5.

One day?

And there was evening and there was morning, a second day. Genesis 1.8.

A second day?

There was evening and there was morning, a third day. Genesis 1.13.

A third day?

There was evening and there was morning, a fourth day. Genesis 1.19.

A fourth day?

There was evening and there was morning, a fifth day. Genesis 1.23.

A fifth day?

And there was evening and there was morning, the sixth day. Genesis 1.31.

The sixth day.

The NASB was influenced by the Revisers in 1884. Why they needed to deviate the wording from the faithful Authorized Version in the first five verses above, is quite beyond me!

"And there was evening and there was morning, one day." Could that not be said of any day? How much doubt does a seemingly innocuous change as this put into the mind of one reading the NASB?

On Genesis 1.5, the 1611 Authorized Version reads:

And the evening and the morning were the first day. (my emphasis). This was the "first day" of creation. The rules of basic grammar tell us that the "the" in "the first day" makes that day the definite article.