Iran’s foreign ministry announced on Sunday that the the P5+1 negotiations scheduled to end on June 30 will have to be extended. With the announcement, Iranian foreign minister Mohammad Javad Zarif returned to Tehran Sunday night to consult with the country’s leadership. A senior U.S. official said that “some progress” had been made, but that “a number of unresolved issues remain”—boilerplate language that has remained virtually unchanged since the April 2 interim agreement was signed in Lausanne.The pace of sanctions relief appears to be the sticking point but Iran’s Western interlocutors appear to be holding firm—for now. British Foreign Secretary Phillip Hammond appeared to be digging in his heels: “No deal is better than a bad deal,” he said. Meanwhile, a senior U.S. diplomat suggested that it would be “really absurd” to think that America would cave after negotiating for this long. (Much like being cool, if you have to say so…)The slippage of the June 30 deadline is not entirely unexpected, nor really all that consequential. But coming up shortly is a deadline of real consequence: July 9. If the Administration does not submit an agreement to Congress by then, the review period under Corker-Menendez extends from 30 to 60 days. During that time, the Administration cannot by law lift sanctions, while Congress reviews and possibly votes on the deal.The extended timeline was created to make sure Iran (or, cynics might suggest, the Administration) could not take advantage of Congress’ August recess to force a quick vote (or, heaven forfend, a recall). Now, though, the legal deadline’s consequences might be felt in Geneva.Holidays, high diplomacy, and warfare have a long, strange history. The tempo of crises during the run-ups to both World War I and World War II were dictated in part by the British Parliament’s vacation schedule, and as many diplomats can tell you, a truly sophisticated understanding of international affairs includes understanding that sometimes crises are flubbed because everyone is simply at the beach (or eating Thanksgiving turkey, etc.)As we get further into the summer, we start running into a bunch of these: July 4 weekend (i.e. July 3), the Congressional recess starting on August 4, Labor Day. Look for them (plus the July 9 deadline) to create unexpected bumps and disruptions in negotiations—or, if Iran is as canny as they’ve proven to be so far, for Tehran to use them as times to test and probe the U.S. position, diplomatically or otherwise.