Seasonal-lottery reservations winners did not claim, reservable from 10 a.m. MT on the 15th of the month after the lottery.
Zion's own Left Fork (Subway) page says winners must claim their reservation within two weeks of the results email, and unclaimed reservations become reservable on the 15th of the month following the lottery at 10am Mountain Time: December 15, March 15, June 15 and September 15 in its table. Cancellations show on the same Recreation.gov seasonal lottery page.
Updated , checked by hand against the target's own page.
No upcoming date is published yet. A watch here alerts you only once a date is recorded on this page.
More openings to watch in Utah
Watched from nps.gov, the target's own public page — not a reservation system we poll.