| 1 | /** |
| 2 | * Times in the reader's own zone. The zone comes from Cloudflare's guess |
| 3 | * for the request (`request.cf.timezone`), or a `g1t_tz` cookie when the |
| 4 | * reader has one; anything unknown is UTC. Every time shown carries its |
| 5 | * zone's abbreviation, and `<time datetime>` keeps the UTC instant. No |
| 6 | * Workers imports, so it is tested under Node. |
| 7 | */ |
| 8 | |
| 9 | export const ZONE_COOKIE = "g1t_tz"; |
| 10 | |
| 11 | const MONTHS = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]; |
| 12 | |
| 13 | /** Whether `tz` is a time zone this runtime knows. */ |
| 14 | export function validZone(tz: unknown): tz is string { |
| 15 | if (typeof tz !== "string" || !tz || tz.length > 64) return false; |
| 16 | try { |
| 17 | new Intl.DateTimeFormat("en-US", { timeZone: tz }); |
| 18 | return true; |
| 19 | } catch { |
| 20 | return false; |
| 21 | } |
| 22 | } |
| 23 | |
| 24 | function cookie(header: string | null | undefined, name: string): string | null { |
| 25 | for (const part of (header ?? "").split(";")) { |
| 26 | const [k, ...v] = part.trim().split("="); |
| 27 | if (k === name) { |
| 28 | try { |
| 29 | return decodeURIComponent(v.join("=")); |
| 30 | } catch { |
| 31 | return null; |
| 32 | } |
| 33 | } |
| 34 | } |
| 35 | return null; |
| 36 | } |
| 37 | |
| 38 | /** The reader's zone: their cookie, else Cloudflare's guess, else UTC. */ |
| 39 | export function readZone(cookieHeader: string | null | undefined, cfTimezone: unknown): string { |
| 40 | const chosen = cookie(cookieHeader, ZONE_COOKIE); |
| 41 | if (validZone(chosen)) return chosen; |
| 42 | return validZone(cfTimezone) ? cfTimezone : "UTC"; |
| 43 | } |
| 44 | |
| 45 | /** The zone's short name at that moment: "PDT", "CEST", "BST", or "UTC+9" where there is no common one. */ |
| 46 | export function zoneAbbr(date: Date, tz: string): string { |
| 47 | if (tz === "UTC" || tz === "Etc/UTC" || tz === "Etc/GMT") return "UTC"; |
| 48 | let offset = ""; |
| 49 | for (const locale of ["en-US", "en-GB"]) { |
| 50 | const name = new Intl.DateTimeFormat(locale, { timeZone: tz, timeZoneName: "short" }).formatToParts(date).find((p) => p.type === "timeZoneName")?.value ?? ""; |
| 51 | if (name && !/^(GMT|UTC)[+-−]/.test(name)) return name; |
| 52 | offset ||= name; |
| 53 | } |
| 54 | return offset.replace(/^GMT/, "UTC") || "UTC"; |
| 55 | } |
| 56 | |
| 57 | /** The wall-clock parts of a moment in a zone. */ |
| 58 | function parts(date: Date, tz: string) { |
| 59 | const got = Object.fromEntries( |
| 60 | new Intl.DateTimeFormat("en-US", { timeZone: tz, year: "numeric", month: "numeric", day: "numeric", hour: "2-digit", minute: "2-digit", hourCycle: "h23" }) |
| 61 | .formatToParts(date) |
| 62 | .map((p) => [p.type, p.value]), |
| 63 | ); |
| 64 | return { year: Number(got.year), month: Number(got.month), day: Number(got.day), hh: String(got.hour).padStart(2, "0"), mm: got.minute }; |
| 65 | } |
| 66 | |
| 67 | /** "6 Oct 2026, 00:25 PDT". */ |
| 68 | export function timeIn(at: string | Date, tz = "UTC"): string { |
| 69 | const date = new Date(at); |
| 70 | const p = parts(date, tz); |
| 71 | return `${p.day} ${MONTHS[p.month - 1]} ${p.year}, ${p.hh}:${p.mm} ${zoneAbbr(date, tz)}`; |
| 72 | } |
| 73 | |
| 74 | /** "6 Oct 00:25 PDT": shorter, for lines that already say the year. */ |
| 75 | export function stampIn(at: string | Date, tz = "UTC"): string { |
| 76 | const date = new Date(at); |
| 77 | const p = parts(date, tz); |
| 78 | return `${p.day} ${MONTHS[p.month - 1]} ${p.hh}:${p.mm} ${zoneAbbr(date, tz)}`; |
| 79 | } |