'First Day' in the Bible

Now in the eleventh year, on the first day of the month, the word of the Lord came to me, saying,

Now in the twenty-seventh year, in the first month, on the first day of the month, the word of the Lord came to me, saying,

Now in the eleventh year, in the third month, on the first day of the month, the word of the Lord came to me, saying,

And it came about in the twelfth year, in the twelfth month, on the first day of the month, that the word of the Lord came to me, saying,

This is what the Lord has said: In the first month, on the first day of the month, you are to take a young ox without any mark on him, and you are to make the holy place clean.