mirror of
https://github.com/AvengeMedia/DankMaterialShell.git
synced 2026-10-13 23:04:04 -04:00
Adolfo Ochagavía
e4793327b8
Root cause: we were creating a `Date` that did not exist in my timezone (Santiago, Chile) because of DST. The JS engine decided to pick the previous day, so I ended up with two times 5 September. Fix: introduce a `DateOnly` object that internally uses UTC (to prevent DST issues). Other parts of the system still use `Date`, which probably should be refactored to use `DateOnly` as well (maybe in an upcoming PR?). In the meantime, we provide a function to export a `DateOnly` as a `Date`, using noon as the time instead of midnight (because there are no DST changes at noon AFAIK). We tested this manually (see the attached screenshots), but didn't find a suitable place for automated tests. port 1.6
69 lines
2.0 KiB
JavaScript
69 lines
2.0 KiB
JavaScript
.pragma library
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// A calendar date with no time and no timezone.
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//
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// Arithmetic runs through Date.UTC, which has no DST gaps, so day and month
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// rollover is exact. Instances are immutable: every operation returns a new one.
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// month is 0-based, matching Javascripts' Date behavior.
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class DateOnly {
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constructor(year, month, day) {
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this.year = year;
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this.month = month;
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this.day = day;
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}
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addDays(days) {
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return _fromUtc(new Date(Date.UTC(this.year, this.month, this.day + days)));
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}
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addMonths(months) {
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const target = new Date(Date.UTC(this.year, this.month + months, 1));
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const lastDay = new Date(Date.UTC(target.getUTCFullYear(), target.getUTCMonth() + 1, 0)).getUTCDate();
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return new DateOnly(target.getUTCFullYear(), target.getUTCMonth(), Math.min(this.day, lastDay));
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}
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// 0 = Sunday, matching Date.getDay().
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dayOfWeek() {
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return new Date(Date.UTC(this.year, this.month, this.day)).getUTCDay();
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}
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daysUntil(other) {
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const from = Date.UTC(this.year, this.month, this.day);
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const to = Date.UTC(other.year, other.month, other.day);
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return Math.round((to - from) / 86400000);
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}
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equals(other) {
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if (!other)
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return false;
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return this.year === other.year && this.month === other.month && this.day === other.day;
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}
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// Local noon, so consumers that read local calendar fields land on this date
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// even on days where local midnight does not exist.
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toDate() {
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return new Date(this.year, this.month, this.day, 12);
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}
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}
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function _fromUtc(date) {
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return new DateOnly(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate());
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}
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function of(year, month, day) {
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return new DateOnly(year, month, day);
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}
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function fromDate(date) {
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return new DateOnly(date.getFullYear(), date.getMonth(), date.getDate());
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}
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function firstOfMonth(year, month) {
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return new DateOnly(year, month, 1);
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}
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function lastOfMonth(year, month) {
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return _fromUtc(new Date(Date.UTC(year, month + 1, 0)));
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}
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