The construction of the Temple began in the month of Ziv, which is identified as the second month:
In the four hundred and eightieth year after the people of Israel came out of the land of Egypt, in the fourth year of Solomon's reign over Israel, in the month (בְּחֹ֣דֶשׁ) of Ziv, which is the second month (הַחֹ֣דֶשׁ), he began to build the house of the LORD. (1 Kings 6:1) [ESV]
Two other events are recorded as occurring in a named month:
And in the eleventh year, in the month (בְּיֶ֣רַח) of Bul, which is the eighth month (הַחֹ֣דֶשׁ), the house was finished in all its parts, and according to all its specifications. He was seven years in building it. (1 Kings 6:38)
And all the men of Israel assembled to King Solomon at the feast in the month (בְּיֶ֥רַח) Ethanim, which is the seventh month (הַחֹ֥דֶשׁ). (1 Kings 8:2)
Finally, Ziv is used a second time:
In the fourth year the foundation of the house of the LORD was laid, in the month (בְּיֶ֖רַח) of Ziv.
(1 Kings 6:37)
Now, like Bul and Ethanim, Ziv is called a יֶרַח month.
Why are the different words for month used? Why is the "month" of Ziv different from the "months" of Bul and Ethanim when identified by number?