A critical moment in the history of the Babylonian exile sets the stage as the Babylonian Empire collapses and power shifts to Media and Persia. The exiled Judeans are filled with anticipation, expecting the prophetic promise of their return to materialize, yet reality sets in as the ultimate redemption is delayed. This period marks the very first year Darius assumes control over the entire global empire, not just his original local kingdom [יוסף אבן יחיא]. Alternatively, this specific timing is reiterated simply to anchor the unfolding events after a lengthy narrative [מצודת דוד].
Seeking answers, Daniel deeply studies the prophetic records, focusing specifically on the calculations and numbers regarding the seventy years foretold by the prophet Jeremiah [רש"י, מצודת ציון]. The primary approach among commentators is that Daniel was calculating the end of this period and realized he had made an error. Initially, he believed the seventy-year countdown began with the very first conquest and the start of the Babylonian subjugation. By this math, the seventy years concluded exactly as the Babylonian Empire fell. Because of this, Daniel expected to witness an immediate, complete redemption and the rebuilding of the Temple [רש"י, אבן עזרא, מצודת דוד, ביאור שטיינזלץ].
When Babylon fell but the Temple remained in ruins, Daniel reevaluated the prophecies and discovered a more complex timeline. He realized the seventy years involved two distinct milestones. The first milestone was the end of Babylonian rule and the initial return of the exiles, which indeed happened exactly seventy years after the subjugation began. However, the complete redemption and the actual rebuilding of the ruined city of Jerusalem would only be counted from the absolute destruction of the city itself. This final destruction occurred eighteen or nineteen years after the initial conquest [רש"י, אבן עזרא, מצודת דוד].
A complementary perspective suggests Daniel consulted two separate prophecies. One regarded the fall of Babylon, and another specifically concerned the ruins of Jerusalem. He understood that while the fixed time for Babylon's collapse had come, the ultimate redemption depended heavily on the merits of the Israelites. Haunted by earlier visions of a prolonged exile, Daniel feared that the people's sins might have caused God to withdraw His promise. This profound fear, combined with his corrected understanding of the timeline, drove Daniel to immediately seek God in prayer, pleading for mercy to hasten the final redemption [מלבי"ם, אלשיך].