'Three Days' in the Bible

The king said to Amasa, “Summon the men of Judah to me within three days and be here yourself.”

So Gad went to David, told him the choices, and asked him, “Do you want three years of famine to come on your land, to flee from your foes three months while they pursue you, or to have a plague in your land three days? Now, think it over and decide what answer I should take back to the One who sent me.”