'First Day' in the Bible

For seven days you must eat bread made without yeast. Surely on the first day you must put away yeast from your houses because anyone who eats bread made with yeast from the first day to the seventh day will be cut off from Israel.

On the first day there will be a holy convocation, and on the seventh day there will be a holy convocation for you. You must do no work of any kind on them, only what every person will eat -- that alone may be prepared for you.

In the first month, from the fourteenth day of the month, in the evening, you will eat bread made without yeast until the twenty-first day of the month in the evening.

"On the first day of the first month you are to set up the tabernacle, the tent of meeting.

So the tabernacle was set up on the first day of the first month, in the second year.