'Of The Month' in the Bible

And David said unto Jonathan, "Behold, tomorrow is the first day of the month, and I should sit with the king at meat. But let me go that I may hide myself in the fields unto this day three days at evening.

And it came to pass on the morrow, which was the second day of the month, that David's place was empty: and Saul said unto Jonathan his son, Wherefore cometh not the son of Jesse to meat, neither yesterday, nor to day?

So Jonathan arose from the table in fierce anger, and did eat no meat the second day of the month: for he was grieved for David, because his father had done him shame.