From b4eff256360c07c532339526d47d1fced01d55ca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Efra=C3=ADn=20Roch=C3=ADn?= <roae.85@gmail.com>
Date: Fri, 2 Jun 2023 13:17:53 -0700
Subject: [PATCH] fix: Issues with calendar sync at the beginning and end of
 month (#9282)
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* increases the time range to cover all time zones

* remove console.log

---------

Co-authored-by: Omar López <zomars@me.com>
---
 .../pages/[user]/calendar-cache/[month].tsx   | 19 ++++++++++---------
 packages/core/CalendarManager.ts              |  6 +++++-
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/apps/web/pages/[user]/calendar-cache/[month].tsx b/apps/web/pages/[user]/calendar-cache/[month].tsx
index 9cd9359bb5..b8b4acb7d6 100644
--- a/apps/web/pages/[user]/calendar-cache/[month].tsx
+++ b/apps/web/pages/[user]/calendar-cache/[month].tsx
@@ -3,15 +3,13 @@
  * caching system that NextJS uses SSG pages.
  * TODO: Redirect to user profile on browser
  */
-import type { GetStaticPaths, GetStaticProps } from "next";
+import type { GetStaticPaths, GetStaticProps, InferGetStaticPropsType } from "next";
 import { z } from "zod";
 
 import { getCachedResults } from "@calcom/core";
 import dayjs from "@calcom/dayjs";
 import prisma from "@calcom/prisma";
 
-const CalendarCache = () => <div />;
-
 const paramsSchema = z.object({ user: z.string(), month: z.string() });
 export const getStaticProps: GetStaticProps<
   { results: Awaited<ReturnType<typeof getCachedResults>> },
@@ -29,16 +27,16 @@ export const getStaticProps: GetStaticProps<
       selectedCalendars: true,
     },
   });
-  const startDate = (
-    dayjs(month, "YYYY-MM").isSame(dayjs(), "month") ? dayjs.utc() : dayjs.utc(month, "YYYY-MM")
-  ).startOf("day");
-  const endDate = startDate.endOf("month");
+  // Subtract 11 hours from the start date to avoid problems in UTC- time zones.
+  const startDate = dayjs.utc(month, "YYYY-MM").startOf("day").subtract(11, "hours").format();
+  // Add 14 hours from the start date to avoid problems in UTC+ time zones.
+  const endDate = dayjs.utc(month, "YYYY-MM").endOf("month").add(14, "hours").format();
   try {
     const results = userWithCredentials?.credentials
       ? await getCachedResults(
           userWithCredentials?.credentials,
-          startDate.format(),
-          endDate.format(),
+          startDate,
+          endDate,
           userWithCredentials?.selectedCalendars
         )
       : [];
@@ -64,5 +62,8 @@ export const getStaticPaths: GetStaticPaths = () => {
     fallback: "blocking",
   };
 };
+type Props = InferGetStaticPropsType<typeof getStaticProps>;
+const CalendarCache = (props: Props) =>
+  process.env.NODE_ENV === "development" ? <pre>{JSON.stringify(props, null, "  ")}</pre> : <div />;
 
 export default CalendarCache;
diff --git a/packages/core/CalendarManager.ts b/packages/core/CalendarManager.ts
index 99bc55240e..592ff2cb5d 100644
--- a/packages/core/CalendarManager.ts
+++ b/packages/core/CalendarManager.ts
@@ -231,7 +231,11 @@ export const getBusyCalendarTimes = async (
   const months = getMonths(dateFrom, dateTo);
   try {
     if (coldStart) {
-      results = await getCachedResults(withCredentials, dateFrom, dateTo, selectedCalendars);
+      // Subtract 11 hours from the start date to avoid problems in UTC- time zones.
+      const startDate = dayjs(dateFrom).subtract(11, "hours").format();
+      // Add 14 hours from the start date to avoid problems in UTC+ time zones.
+      const endDate = dayjs(dateTo).endOf("month").add(14, "hours").format();
+      results = await getCachedResults(withCredentials, startDate, endDate, selectedCalendars);
       logger.info("Generating calendar cache in background");
       // on cold start the calendar cache page generated in the background
       Promise.all(months.map((month) => createCalendarCachePage(username, month)));