'First Day' in the Bible

It happened, that in the eleventh year, and the first day of the Month, the word of the LORD came unto me, saying,

In the twenty seventh year, the first day of the first Month, came the word of the LORD unto me, saying,

Moreover, it happened in the eleventh year, the first day of the third Month, that the word of the LORD came unto me, saying,

In the twelfth year, the first day of the twelfth Month, the word of the LORD came unto me, saying,

Thus sayeth the LORD God: The first day of the first month thou shalt take a young bullock without blemish, and cleanse the Sanctuary.