en_tn/gen/01/19.md

evening and morning

This refers to the whole day. The writer speaks of the whole day as if it were these two parts. In the Jewish culture, a day begins when the sun sets. See how you translated this in Genesis 1:5. (See: rc://en/ta/man/translate/figs-merism)

the fourth day

This refers to the fourth day that the universe existed. See how you translated "the first day" in Genesis 1:5 and decide if you should translate this the same way.