Daniel 9:1-3

In the first year of Darius the son of Ahasuerus, of Median descent, who was made king over the realm of the Chaldeans— in the first year of his reign, I, Daniel, understood from the books the number of years which, according to the word of the LORD to Jeremiah the prophet, must pass before the desolations [which had been] pronounced on Jerusalem would end; and it was seventy years. [Jer 25:11, 12; 29:10] So I directed my attention to the Lord God to seek Him by prayer and supplications, with fasting, sackcloth and ashes.