38 lines
1.2 KiB
TypeScript
38 lines
1.2 KiB
TypeScript
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/**
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* Date labels for the Schedule tab. Calendar dates are formatted in UTC from
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* their components, so the printed day never shifts with the viewer's offset.
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*/
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import { dayNumber } from "./cycle";
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const LOCALE = "en-US";
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function utcDate(iso: string): Date {
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return new Date(dayNumber(iso) * 86_400_000);
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}
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function format(iso: string, options: Intl.DateTimeFormatOptions): string {
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return new Intl.DateTimeFormat(LOCALE, { ...options, timeZone: "UTC" }).format(utcDate(iso));
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}
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/** "Tuesday, Sep 1" */
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export function anchorLabel(iso: string): string {
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return `${format(iso, { weekday: "long" })}, ${format(iso, { month: "short", day: "numeric" })}`;
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}
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/** "September 2026" */
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export function monthLabel(iso: string): string {
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return format(iso, { month: "long", year: "numeric" });
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}
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/** "Sep 4" */
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export function shortDate(iso: string): string {
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return format(iso, { month: "short", day: "numeric" });
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}
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/** "Sep 4 – 7", "Sep 28 – Oct 2", or "Sep 4" for a single day. */
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export function dateRange(start: string, end: string): string {
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if (start === end) return shortDate(start);
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const sameMonth = start.slice(0, 7) === end.slice(0, 7);
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return `${shortDate(start)} – ${sameMonth ? Number(end.slice(8)) : shortDate(end)}`;
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}
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