Seeking to put some distance between himself and the diplomatic drama back in Washington, US President Barack Obama departed for Great Britain this week, where he made a highly revealing mistake.After visiting Westminster Abbey and laying a wreath on the Grave of the Unknown Soldier, Obama signed the guest book.“It is a great privilege to commemorate our common heritage and common sacrifice,” he wrote, before signing his name and adding the date: “24 May 2008.”2008?! That was three years ago! Even the liberals over at The New Yorker could not help themselves, taunting the commander-in-chief with the headline: “President Obama has no idea what year it is.” Now all of us, of course, have our “senior moments” – flashes of forgetfulness about where the car keys we were holding five minutes ago have gone. And who hasn’t had the awkward experience of periodically having to ponder that most Socratic of all musings: Is today Tuesday or Wednesday? Nonetheless, Obama’s slip-up is more than a momentary lapse. It is an illuminating incident that reveals a lot about the American president.I’m no psychologist, but I’d say Obama is clearly looking back longingly to the days when he was a candidate whose only responsibility was to smile for the cameras and deliver speeches. Indeed, it almost seems like he was trying to reorder reality.Such an attitude may be very human, but it isn’t quite presidential. A leader is someone who must grapple with today while planning for tomorrow. Life is not a Michael J. Fox movie, and there are no time machines that allow us to go back to the future.Yet this fantasy is precisely what seems to guide the president’s policy on the Arab-Israeli conflict. In his address to AIPAC, Obama asserted that “the borders of Israel and Palestine should be based on the 1967 lines, with mutually agreed swaps” – reiterating remarks he made at the State Department last week.In other words, he would simply like to travel back to before the 1967 Six Day War began, ignoring the lessons of that conflict and its outcome.Such a suggestion is not only naïve, but also dangerous.If Israelis learned anything from that encounter, it is that the pre-1967 frontiers were an invitation to potential extermination. They were indefensible and untenable and only served to whet our foes’ appetite for war.Remember, in the run-up to the fighting, the Arab leaders made it chillingly clear that their aim was to destroy the Jewish state.On May 20, 1967, Hafez Assad (then serving as Syria’s defense minister) said: “Our forces are now entirely ready to initiate the act of liberation itself, and to explode the Zionist presence in the Arab homeland. I, as a military man, believe that the time has come to enter into a battle of annihilation.”On May 26, Egyptian president Gamal Nasser declared in a speech to his nation: “Our basic aim will be to destroy Israel.”And at a press conference the following day, PLO founder Ahmad Shukeiry said: “D-Day is approaching. The Arabs have waited 19 years for this, and will not flinch from the war of liberation.”On May 30, Cairo Radio was even more explicit: “Israel has two choices, both of which are drenched with Israeli blood: Either it will be strangled by the Arab military and economic siege, or it will be killed by the bullets of the Arab armies surrounding it from the south, from the north and from the east.”A week later, the war began. And a week after that, it had ended, leaving Israel in control of Judea, Samaria, Gaza and the Golan Heights.In 1967, the State of Israel was faced with the threat of extinction. It fought off its enemies and liberated the cradle of ancient Jewish civilization, reuniting Jerusalem and depriving our enemies of the platform from which they had sought to destroy us.By invoking the pre-’67 lines, Obama has essentially said that all this didn’t matter, and that Israel’s acquisition of territory in an act of pure self-defense was somehow illegitimate.He would like to simply push the “rewind” button, returning the Jewish state to an unsustainable vulnerability.But this attempt at time travel is little more than political science fiction. It is pure illusion and, as Prime Minister Binyamin Netanyahu made so eloquently clear in his address to Congress on Tuesday, it cannot and will not happen.As much as Obama might wish to brush aside the past, that would be an insult to history and a menace to our destiny.So let’s get one thing straight: Israel did not “occupy” Judea and Samaria – we won that territory, fair and square. The war of 1967 was one that Israel neither asked for nor initiated. But with God’s help we won it. And we will never go back to what came before.It’s 2011, Mr. President. Get used to it.The writer serves as chairman of Shavei Israel (www.shavei.org), a Jerusalem-based organization that assists ‘lost Jews’ seeking to return to the Jewish people.