Gen 1:5: yom, evening and morning

Says God calls the light יוֹם (yom) and the darkness לָיְלָה (1:5), so the word first names daylight. BDB glosses it "day" and also gives "= time." Each of the six days closes וַיְהִי־עֶרֶב וַיְהִי־בֹקֶר; BDB glosses the nouns "(sun)set, evening" and "morning."

Says Day one is יוֹם אֶחָד (yom echad), a cardinal with no article; the BSB's "the first day" supplies an ordinal and an article. Days two to five have ordinals without the article (יוֹם שֵׁנִי, 1:8). Day six is יוֹם הַשִּׁשִּׁי: the article stands on the ordinal only. The seventh day of 2:2–3 (context only) has no evening–morning line. In Gen 2:4, בְּיוֹם עֲשׂוֹת ("in the day that," BSB) covers the whole making.

Uncertain How long the days are and how the week is to be read are not decided by these data. Five views are held: ordinary days, long ages, a literary framework, days by analogy with a human week, and a temple-inauguration reading. They are set out on equal terms in note.exegetical.Gen.1.1-Gen.1.31.creation-days-views; see also xref.Gen.1.31.Exod.20.11.heb. No lean is taken here.