But that goes back to the days before computers when you could book a flight more than 360 days in advance
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The BEACON Univac computer system of British European fame would happily book 18 months in advance. ( in the 1960s ). Many bookings for "Wakes weeks" were made that far in advance.
All the many IBM based airline reservations systems that I worked with could only cope with about 360 days in advance i.e. a year minus a few days.