Certain weekends on the American calendar are claimed years in advance and defended vigorously. Their value comes from a combination of school schedules, an extra day and a shortage of alternatives.
An extra day changes the arithmetic
A federal holiday attached to a weekend adds a full day of matinee-heavy attendance, and that day performs closer to a Saturday than to a Monday.
Opening totals are reported across the four days, producing a headline figure larger than a comparable weekend would generate.
Since the reported opening drives coverage and perceived momentum, the extra day matters beyond the tickets it sells.
School calendars supply the audience
Long weekends often coincide with school breaks in many districts, which frees the family audience for daytime showings across several consecutive days.
Films aimed at that audience depend on matinees, and matinee capacity is the scarce resource during a normal weekend.
A holiday weekend effectively multiplies the available showtimes for exactly the films that need them most, since a theater can run daytime screenings on days it would otherwise sell lightly.
Districts do not break in unison, so the effect is spread rather than uniform, but it is large enough that family releases are routinely built around these dates.
Claiming a date is a public act
Studios announce release dates years ahead, and the announcement functions as a claim that discourages others from placing similar films opposite.
Competitors respond by moving, since two comparable films sharing a weekend split an audience neither can fully serve.
The calendar therefore settles into an arrangement where each major date has an occupant and challengers position around it.
Dates move for reasons unrelated to quality
A film can shift when a competitor claims the same weekend, when postproduction runs long or when a marketing campaign needs more time.
Moves are read publicly as signals of trouble, though the more common causes are scheduling and competition rather than the film itself.
Studios manage that perception carefully, which is why moves are frequently announced alongside other, more positive news.
Holding a date has its own cost
A film locked to a valuable weekend must be finished for it, which constrains editing, effects work and the ability to respond to test screenings.
Effects-heavy productions in particular face a hard stop, since the date drives the delivery schedule for every vendor involved.
The weekend that makes a film's opening also determines how much time its makers had to finish it, and that tradeoff is made long before anyone knows whether it was worth taking.