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fix(caldav): use toJSDate instead of toString to prevent timezone double-conversion #28796

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fix(caldav): use toJSDate instead of toString to prevent timezone double-conversion #28796

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160 changes: 160 additions & 0 deletions packages/lib/CalendarService.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,9 @@ vi.mock("./CalEventParser", () => ({
getRichDescription: vi.fn().mockReturnValue("Test Description"),
}));

import dayjs from "@calcom/dayjs";
import type { CalendarServiceEvent } from "@calcom/types/Calendar";
import ICAL from "ical.js";
import BaseCalendarService from "./CalendarService";

const createMockEvent = (overrides: Partial<CalendarServiceEvent> = {}): CalendarServiceEvent => ({
Expand Down Expand Up @@ -748,3 +750,161 @@ describe("CalendarService - SCHEDULE-AGENT injection", () => {
});
});
});

describe("CalendarService - CalDAV event time parsing", () => {
/**
* Helper that mirrors the getEvents() parsing logic.
* Accepts a raw iCal string and returns { startDate, endDate } using the given strategy.
*/
function parseDates(icalString: string, strategy: "buggy" | "fixed") {
const jcalData = ICAL.parse(icalString);
const vcalendar = new ICAL.Component(jcalData);
const vevent = vcalendar.getFirstSubcomponent("vevent");
const event = new ICAL.Event(vevent);

const vtimezone = vcalendar.getFirstSubcomponent("vtimezone");
const calendarTimezone = vtimezone?.getFirstPropertyValue<string>("tzid") || "";

if (strategy === "buggy") {
// Current code in getEvents() — double conversion
const startDate = calendarTimezone
? dayjs.tz(event.startDate.toString(), calendarTimezone)
: new Date(event.startDate.toUnixTime() * 1000);
const endDate = calendarTimezone
? dayjs.tz(event.endDate.toString(), calendarTimezone)
: new Date(event.endDate.toUnixTime() * 1000);
return {
startMs: startDate.valueOf(),
endMs: endDate.valueOf(),
};
}

// Fixed: convertToZone + toJSDate (same pattern as getAvailability)
if (vtimezone) {
const zone = new ICAL.Timezone(vtimezone);
event.startDate = event.startDate.convertToZone(zone);
event.endDate = event.endDate.convertToZone(zone);
}
const startDate = calendarTimezone
? new Date(event.startDate.toJSDate())
: new Date(event.startDate.toUnixTime() * 1000);
const endDate = calendarTimezone
? new Date(event.endDate.toJSDate())
: new Date(event.endDate.toUnixTime() * 1000);
return {
startMs: startDate.valueOf(),
endMs: endDate.valueOf(),
};
}

const zimbraUtcIcal = [
"BEGIN:VCALENDAR",
"BEGIN:VTIMEZONE",
"TZID:Europe/Berlin",
"BEGIN:STANDARD",
"DTSTART:19701025T030000",
"TZOFFSETFROM:+0200",
"TZOFFSETTO:+0100",
"RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10",
"END:STANDARD",
"BEGIN:DAYLIGHT",
"DTSTART:19700329T020000",
"TZOFFSETFROM:+0100",
"TZOFFSETTO:+0200",
"RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3",
"END:DAYLIGHT",
"END:VTIMEZONE",
"BEGIN:VEVENT",
"DTSTART:20240115T083000Z",
"DTEND:20240115T084500Z",
"SUMMARY:Zimbra Meeting",
"UID:test-zimbra-utc@example.com",
"END:VEVENT",
"END:VCALENDAR",
].join("\r\n");

const tzidRefIcal = [
"BEGIN:VCALENDAR",
"BEGIN:VTIMEZONE",
"TZID:Europe/Berlin",
"BEGIN:STANDARD",
"DTSTART:19701025T030000",
"TZOFFSETFROM:+0200",
"TZOFFSETTO:+0100",
"RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10",
"END:STANDARD",
"BEGIN:DAYLIGHT",
"DTSTART:19700329T020000",
"TZOFFSETFROM:+0100",
"TZOFFSETTO:+0200",
"RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3",
"END:DAYLIGHT",
"END:VTIMEZONE",
"BEGIN:VEVENT",
"DTSTART;TZID=Europe/Berlin:20240115T093000",
"DTEND;TZID=Europe/Berlin:20240115T094500",
"SUMMARY:Berlin Meeting",
"UID:test-berlin-tz@example.com",
"END:VEVENT",
"END:VCALENDAR",
].join("\r\n");

it("buggy code: UTC times with VTIMEZONE produce wrong timestamps", () => {
// Reproduces #27877: Zimbra CalDAV events with UTC times + VTIMEZONE
const { startMs, endMs } = parseDates(zimbraUtcIcal, "buggy");
const durationMs = endMs - startMs;

// The buggy code shifts both dates by the tz offset, but since the
// original times are UTC and toString() strips the Z, dayjs.tz
// re-interprets them as local Berlin time → wrong absolute timestamps.
// The duration is still 15min (both shifted equally), but the
// absolute times are wrong.
const expectedStartUtcMs = Date.UTC(2024, 0, 15, 8, 30, 0);
expect(startMs).not.toBe(expectedStartUtcMs);

// Duration happens to stay 15min here because both are shifted equally,
// but the absolute time is wrong — which causes issues downstream.
expect(durationMs).toBe(15 * 60 * 1000);
});

it("fixed code: UTC times with VTIMEZONE produce correct 15min duration", () => {
const { startMs, endMs } = parseDates(zimbraUtcIcal, "fixed");

expect(endMs).toBeGreaterThan(startMs);
expect(endMs - startMs).toBe(15 * 60 * 1000);

// Absolute times should be correct: 08:30 UTC
const expectedStartUtcMs = Date.UTC(2024, 0, 15, 8, 30, 0);
expect(startMs).toBe(expectedStartUtcMs);
});

it("fixed code: TZID-referenced times produce correct 15min duration", () => {
const { startMs, endMs } = parseDates(tzidRefIcal, "fixed");

expect(endMs).toBeGreaterThan(startMs);
expect(endMs - startMs).toBe(15 * 60 * 1000);

// 09:30 Berlin in January = UTC+1 = 08:30 UTC
const expectedStartUtcMs = Date.UTC(2024, 0, 15, 8, 30, 0);
expect(startMs).toBe(expectedStartUtcMs);
});

it("fixed code: events without VTIMEZONE parse correctly", () => {
const noTzIcal = [
"BEGIN:VCALENDAR",
"BEGIN:VEVENT",
"DTSTART:20240115T083000Z",
"DTEND:20240115T084500Z",
"SUMMARY:Simple UTC Meeting",
"UID:test-no-tz@example.com",
"END:VEVENT",
"END:VCALENDAR",
].join("\r\n");

const { startMs, endMs } = parseDates(noTzIcal, "fixed");

expect(endMs).toBeGreaterThan(startMs);
expect(endMs - startMs).toBe(15 * 60 * 1000);
expect(startMs).toBe(Date.UTC(2024, 0, 15, 8, 30, 0));
});
});
17 changes: 13 additions & 4 deletions packages/lib/CalendarService.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -952,15 +952,24 @@ export default abstract class BaseCalendarService implements Calendar {
const vevent = vcalendar.getFirstSubcomponent("vevent");
const event = new ICAL.Event(vevent);

const calendarTimezone =
vcalendar.getFirstSubcomponent("vtimezone")?.getFirstPropertyValue<string>("tzid") || "";
const vtimezone = vcalendar.getFirstSubcomponent("vtimezone");
const calendarTimezone = vtimezone?.getFirstPropertyValue<string>("tzid") || "";

// Register and convert to the VTIMEZONE zone so that toJSDate()
// produces correct UTC timestamps (fixes #27877 — negative durations
// from Zimbra CalDAV where UTC times were re-interpreted as local).
if (vtimezone) {
const zone = new ICAL.Timezone(vtimezone);
event.startDate = event.startDate.convertToZone(zone);
event.endDate = event.endDate.convertToZone(zone);
}

const startDate = calendarTimezone
? dayjs.tz(event.startDate.toString(), calendarTimezone)
? dayjs(event.startDate.toJSDate())
: new Date(event.startDate.toUnixTime() * 1000);

const endDate = calendarTimezone
? dayjs.tz(event.endDate.toString(), calendarTimezone)
? dayjs(event.endDate.toJSDate())
: new Date(event.endDate.toUnixTime() * 1000);

return {
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