From a0184df7b2c7689451b7690b1fb5c0cae70919f4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=84=E4=BA=91=E9=BE=99?=
 <76432572+nankingjing@users.noreply.github.com>
Date: Sat, 11 Jul 2026 19:46:22 +0800
Subject: [PATCH] fix(rollup): compute ISO week from UTC calendar fields

---
 src/rollup.ts | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/rollup.ts b/src/rollup.ts
index bcefdd0..766a830 100644
--- a/src/rollup.ts
+++ b/src/rollup.ts
@@ -51,8 +51,11 @@ function readWeeklyDigest(date: string): string | null {
 
 /** Format a date as ISO week string, e.g. "2026-W10". */
 function toWeekStr(date: Date): string {
-  // ISO week: week containing the first Thursday of the year
-  const d = new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()));
+  // ISO week: week containing the first Thursday of the year.
+  // Read the calendar date via UTC getters: callers pass a CST timestamp whose
+  // UTC fields hold the intended CST date, so local getters would shift the day
+  // (and thus the week/year) whenever the process runs outside UTC.
+  const d = new Date(Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate()));
   d.setUTCDate(d.getUTCDate() + 4 - (d.getUTCDay() || 7));
   const yearStart = new Date(Date.UTC(d.getUTCFullYear(), 0, 1));
   const week = Math.ceil(((d.getTime() - yearStart.getTime()) / 86400000 + 1) / 7);