'First Day' in the Bible

In the first day ye shall have a holy convocation: ye shall do no servile work in it.

Speak to the children of Israel, saying, In the seventh month, in the first day of the month, shall ye have a sabbath, a memorial of blowing of trumpets, a holy convocation.

On the first day shall be a holy convocation: ye shall do no servile work in it.

Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast to the LORD seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath.

And ye shall take you on the first day the boughs of goodly trees, branches of palm-trees, and the boughs of thick trees, and willows of the brook; and ye shall rejoice before the LORD your God seven days.