From 8a7eefb3ec73a4119295715975050f22214a5678 Mon Sep 17 00:00:00 2001
From: "gpt-engineer-app[bot]"
 <159125892+gpt-engineer-app[bot]@users.noreply.github.com>
Date: Fri, 24 Apr 2026 13:59:15 +0000
Subject: [PATCH] Changes

Co-authored-by: renee-png <262607627+renee-png@users.noreply.github.com>
---
 src/lib/workflow-chain.ts | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/lib/workflow-chain.ts b/src/lib/workflow-chain.ts
index 660dedd..ea015b8 100644
--- a/src/lib/workflow-chain.ts
+++ b/src/lib/workflow-chain.ts
@@ -1,5 +1,17 @@
 import { supabase } from "@/integrations/supabase/client";
-import { addDays, format } from "date-fns";
+import { addDays } from "date-fns";
+
+/**
+ * Format a Date as "YYYY-MM-DD" using its UTC components. We do this so that
+ * a `completed_at` UTC timestamp like 2026-04-24T02:00:00Z (which is still
+ * Apr 23 in US local time) doesn't shift the computed due_date back a day.
+ */
+function toUTCDateString(d: Date): string {
+  const y = d.getUTCFullYear();
+  const m = String(d.getUTCMonth() + 1).padStart(2, "0");
+  const day = String(d.getUTCDate()).padStart(2, "0");
+  return `${y}-${m}-${day}`;
+}
 
 /**
  * After a task is marked complete, spawn the next task from its workflow
@@ -48,7 +60,7 @@ export async function spawnNextWorkflowTask(taskId: string): Promise<string | nu
   if (existing) return existing.id;
 
   const baseDate = task.completed_at ? new Date(task.completed_at) : new Date();
-  const dueDate = format(addDays(baseDate, nextTpl.days_from_start ?? 0), "yyyy-MM-dd");
+  const dueDate = toUTCDateString(addDays(baseDate, nextTpl.days_from_start ?? 0));
 
   const { data: created, error } = await supabase
     .from("tasks")
@@ -129,7 +141,7 @@ export async function spawnNextCollectionWorkflowTask(
   if (existing) return existing.id;
 
   const baseDate = ct.done_at ? new Date(ct.done_at) : new Date();
-  const dueDate = format(addDays(baseDate, nextTpl.days_from_start ?? 0), "yyyy-MM-dd");
+  const dueDate = toUTCDateString(addDays(baseDate, nextTpl.days_from_start ?? 0));
 
   const { data: created, error } = await supabase
     .from("collection_tasks")