'Days' in the Bible

Then three years later I did go up to Jerusalem to get acquainted with Cephas (Peter), and I stayed with him fifteen days.

[For example,] you observe [particular] days and months and seasons and years.

Believers, I beg of you, become as I am [free from the bondage of Jewish ritualism and ordinances], for I have become as you are [a Gentile]. You did me no wrong [when I first came to you; do not do it now].