Iran Standard Time (Tehran)

Iran Standard Time (IRST) is UTC+3:30, another of the world's half-hour offset time zones. Iran observes daylight saving time (IRDT, UTC+4:30), but uses the Solar Hijri calendar (based on the astronomical vernal equinox) to determine transition dates, making its DST schedule unique. Tehran, the capital, is a sprawling metropolis of over 9 million people (15 million in the metro area). Iran adopted its half-hour offset in 1945 as a compromise between UTC+3 (Arabian Time) and UTC+4 (Gulf Time), reflecting the country's position between the Arab world and Central Asia. The Tehran Stock Exchange (TSE) is significant in the Middle East and operates on IRST. Iran's timezone isolation (very few other countries use half-hour offsets) reflects its broader geopolitical independence. The country has the world's fourth-largest proven oil reserves and second-largest natural gas reserves. Iran's ancient civilization has contributed enormously to human culture — Persian poetry, mathematics (algebra), and architecture have influenced the world. The bazaars of Isfahan and Tehran still operate on traditional schedules influenced by prayer times and the rhythms of IRST.