Disney dropped the idea for individual ride tickets, replacing them with "passports", charging a single admission price with unlimited access to all attractions, "except shooting galleries". While this idea was not original to Disney, it had business advantages: in addition to guaranteeing that everyone paid the same entry amount regardless of their length of stay or number of rides ridden, the park no longer had to print ride tickets, provide staff for ticket booths, nor provide staff to collect tickets or monitor attractions for people sneaking on without tickets. Later, Disney introduced other entry options such as multi-day passes, Annual Passes (which allow unlimited entry to the Park for an annual fee), and Southern California residents' discounts. In February 2016, Disneyland adopted a demand-based pricing system for single-day admission, charging different prices for "value", "regular", and "peak" days, based on projected attendance. Approximately 30% of days will be designated as "value", mainly weekdays when school is in session, 44% will be designated as "regular", and 26% will be designated as "peak", mostly during holidays and weekends in July. In February 2020, Disneyland switched to a multi-tiered system, initially with 5 pricing tiers, with approximately 64% of days being in Tier 4 and above. A sixth tier was added in October 2021. Before 1982, passport tickets were available to groups only. Closures Disneyland has had six unscheduled closures: In 1963, following the assassination of John F. Kennedy. In 1970, due to an anti-Vietnam riot instigated by the Youth International Party. In 1987, on December 16 due to a winter storm. In 1992, on December 7 due to a winter storm. In 2001, after the September 11 attacks. In 2020–2021, in response to the COVID-19 pandemic and safety protocols, the park closed on March 14, 2020 and reopened on April 30, 2021. Additionally, Disneyland has had numerous planned closures: In the early years, the park was often scheduled to be closed on Mondays and Tuesdays during the off-season. This was in conjunction with nearby Knott's Berry Farm, which closed on Wednesdays and Thursdays to keep costs down for both parks, while offering Orange County visitors a place to go seven days a week. On May 4, 2005, for the 50th Anniversary Celebration media event. The park has closed early to accommodate various special events, such as special press events, tour groups, VIP groups, and private parties. It is common for a corporation