'Three Days' in the Bible

And the king said to Amasa, gather to me the men of Judah within three days, and you be present here.

And Gad came to David, and told him, and said to him, Shall seven years of famine come upon you and on your land? Or will you flee three months before your enemies while they pursue you? Or shall there be three days' plague in your land? And advise, and see what answer I shall return to Him who sent me.