Daniel's seventy weeks begins with the decree to rebuild Jerusalem. The prophecy itself concerns "the holy city". Many eschatologists point to May 14, 1948, when Israel became an independent nation, as "the budding of the fig tree". For the purposes of the seventy weeks, though, some have pointed instead to June 7, 1967, when Israel regained control of Jerusalem from Jordan. The BBC has a wonderful set of maps detailing control of Jerusalem before and after the Six-Day War. The region under Jordanian control before the war included the old walled city containing all the important Jewish, Muslim and Christian religious sites.
On the third day of the war, June 7, Jordanian forces were pushed from the West Bank across the River Jordan. Israel had annexed all of the West Bank and Jerusalem, opening up the old city to Jews for the first time in 2000 years. A UN arranged cease-fire between Israel and Jordan went into effect that evening. In Luke 21:24, Jesus says "...and Jerusalem shall be trodden down of the Gentiles, until the times of the Gentiles be fulfilled." It is crystal clear that the times of the Gentiles were fulfilled June 7, 1967.
What then shall we do? In the same chapter, Jesus advises us:
And take heed to yourselves, lest at any time your hearts be overcharged with surfeiting, and drunkenness, and cares of this life, and [so] that day come upon you unawares. For as a snare shall it come on all them that dwell on the face of the whole earth. Watch ye therefore, and pray always, that ye may be accounted worthy to escape all these things that shall come to pass, and to stand before the Son of man. - Luke 21:34-36
 The Six Day War - Part 1: June 5-7.