Ho New/Reuters/The Atlantic
The April 24, 1984, edition of the British defense publication Jane’s Defence Weekly informed its readers: “Iran is engaged in the production of an atomic bomb, likely to be ready within two years, according to press reports in the Persian Gulf last week.” Subsequent warnings from U.S. and foreign sources about Iran’s imminent acquisition of a nuclear weapon have been offered over the past four decades. These false guesses are worth bearing in mind as news from the nuclear negotiations in Lausanne, Switzerland emerges.

More technical “breakout” estimates—the time it would take Iran to compile enough highly-enriched uranium (HEU) to fuel one nuclear weapon—continue to be published, with slightly varying timelines. Setting aside logic, wisdom, and a huge range of assumptions, if you average these five estimates, Iran would require 89.8 days, or three months, if it made a hypothetical rush for one bombs-worth of HEU.