From 7603c3eb21bd8c4ac2af2485b60e7fe56d36a0e3 Mon Sep 17 00:00:00 2001
From: JCEEE <0xjceee@proton.me>
Date: Tue, 4 Aug 2026 08:46:39 +0100
Subject: [PATCH] add timezone file`

---
 timezone.ts | 164 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 164 insertions(+)
 create mode 100644 timezone.ts

diff --git a/timezone.ts b/timezone.ts
new file mode 100644
index 0000000..a91c10f
--- /dev/null
+++ b/timezone.ts
@@ -0,0 +1,164 @@
+export const AUTO_TZ = "auto";
+export const DEFAULT_TZ = "UTC";
+
+export function resolveTz(tz?: string | null): string {
+  if (tz && tz !== AUTO_TZ) return tz;
+  try {
+    return Intl.DateTimeFormat().resolvedOptions().timeZone || DEFAULT_TZ;
+  } catch {
+    return DEFAULT_TZ;
+  }
+}
+
+export function dateStrInTz(date: Date, tz: string): string {
+  const parts = new Intl.DateTimeFormat("en-US", {
+    timeZone: tz,
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+  }).formatToParts(date);
+  const get = (type: string) =>
+    parts.find((p) => p.type === type)?.value ?? "00";
+  return `${get("year")}-${get("month")}-${get("day")}`;
+}
+
+export function weekdayInTz(date: Date, tz: string): number {
+  const parts = new Intl.DateTimeFormat("en-US", {
+    timeZone: tz,
+    weekday: "short",
+  }).formatToParts(date);
+  const wd = parts.find((p) => p.type === "weekday")?.value ?? "";
+  const map: Record<string, number> = {
+    Sun: 0,
+    Mon: 1,
+    Tue: 2,
+    Wed: 3,
+    Thu: 4,
+    Fri: 5,
+    Sat: 6,
+  };
+  return map[wd] ?? date.getDay();
+}
+
+export function todayInTz(tz: string): string {
+  return dateStrInTz(new Date(), tz);
+}
+
+export function addDaysStr(dateStr: string, days: number): string {
+  const [y, m, d] = dateStr.split("-").map(Number);
+  const dt = new Date(Date.UTC(y, m - 1, d + days));
+  return dt.toISOString().slice(0, 10);
+}
+
+export function weekStart(payday: number, tz: string): string {
+  const today = todayInTz(tz);
+  const wd = weekdayInTz(new Date(), tz);
+  const back = ((wd - payday) % 7 + 7) % 7;
+  return addDaysStr(today, -back);
+}
+
+function monthStartStr(): string {
+  const d = new Date();
+  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}-01`;
+}
+
+function monthEndStr(month?: string): string {
+  if (!month) {
+    const d = new Date();
+    month = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}`;
+  }
+  const [y, m] = month.split("-").map(Number);
+  const lastDay = new Date(y, m, 0).getDate();
+  return `${month}-${String(lastDay).padStart(2, "0")}`;
+}
+
+export function periodStart(period: string, payday: number, tz: string): string {
+  if (period === "daily") return todayInTz(tz);
+  if (period === "weekly") return weekStart(payday, tz);
+  if (period === "monthly") return monthStartStr();
+  return weekStart(payday, tz);
+}
+
+export function periodEnd(period: string, start: string): string {
+  if (period === "daily") return start;
+  if (period === "weekly") return addDaysStr(start, 6);
+  if (period === "monthly") return monthEndStr(start.slice(0, 7));
+  return start;
+}
+
+export function wallClockToUtc(dateStr: string, time: string, tz: string): number {
+  const [y, m, d] = dateStr.split("-").map(Number);
+  const [h, min] = time.split(":").map(Number);
+  let epoch = Date.UTC(y, m - 1, d, h, min);
+  for (let i = 0; i < 4; i++) {
+    const parts = new Intl.DateTimeFormat("en-US", {
+      timeZone: tz,
+      year: "numeric",
+      month: "2-digit",
+      day: "2-digit",
+      hour: "2-digit",
+      minute: "2-digit",
+      hour12: false,
+    }).formatToParts(new Date(epoch));
+    const get = (type: string) =>
+      parts.find((p) => p.type === type)?.value ?? "00";
+    const gotDate = `${get("year")}-${get("month")}-${get("day")}`;
+    let gotHour = parseInt(get("hour"), 10);
+    if (gotHour === 24) gotHour = 0;
+    const gotEpoch = Date.UTC(
+      parseInt(get("year"), 10),
+      parseInt(get("month"), 10) - 1,
+      parseInt(get("day"), 10),
+      gotHour,
+      parseInt(get("minute"), 10),
+    );
+    if (gotEpoch === epoch && gotDate === dateStr) break;
+    epoch = Date.UTC(y, m - 1, d, h, min) + (epoch - gotEpoch);
+  }
+  return epoch;
+}
+
+export const COMMON_TIMEZONES: string[] = [
+  "Europe/London",
+  "Europe/Paris",
+  "Europe/Berlin",
+  "Europe/Madrid",
+  "Europe/Rome",
+  "Europe/Amsterdam",
+  "Europe/Lisbon",
+  "Europe/Dublin",
+  "Europe/Warsaw",
+  "Europe/Stockholm",
+  "Europe/Athens",
+  "Europe/Istanbul",
+  "Europe/Moscow",
+  "America/New_York",
+  "America/Chicago",
+  "America/Denver",
+  "America/Los_Angeles",
+  "America/Toronto",
+  "America/Vancouver",
+  "America/Sao_Paulo",
+  "America/Mexico_City",
+  "Asia/Tokyo",
+  "Asia/Shanghai",
+  "Asia/Hong_Kong",
+  "Asia/Singapore",
+  "Asia/Seoul",
+  "Asia/Kolkata",
+  "Asia/Dubai",
+  "Asia/Jerusalem",
+  "Asia/Bangkok",
+  "Asia/Manila",
+  "Australia/Sydney",
+  "Australia/Melbourne",
+  "Australia/Brisbane",
+  "Australia/Perth",
+  "Australia/Adelaide",
+  "Pacific/Auckland",
+  "Africa/Johannesburg",
+  "Africa/Cairo",
+  "Africa/Lagos",
+  "Africa/Nairobi",
+  "UTC",
+];