For travel in 2026, you can book Shinkansen tickets exactly one month in advance (at 10:00 AM Japan time) through official platforms like the SmartEX app or the JR West website. Booking this early is highly recommended for travel during "peak" periods such as Golden Week, Obon, and New Year’s, when seats—especially those in the "oversized baggage" sections—sell out almost instantly. If you are traveling during a standard weekday, booking 2 to 3 days in advance is usually sufficient to secure a reserved seat. For those who want maximum flexibility, you can also buy "non-reserved" tickets on the day of travel at any station kiosk, which allows you to board any train on your route, though you are not guaranteed a seat. In 2026, the smartEX-round trip discount is scheduled to end on March 31, so travelers after April 1 should focus on early "Hayatoku" advance-purchase discounts to save up to 15-30% on long-haul fares like Tokyo to Hiroshima.