fix: wrong slot starting times for half hour times zones (#10161)

* fix timezone zone issue for first slot

* fix failed test in getSchedule

* Update apps/web/test/lib/getSchedule.test.ts

---------

Co-authored-by: CarinaWolli <wollencarina@gmail.com>
Co-authored-by: alannnc <alannnc@gmail.com>

apps/web/test/lib/getSchedule.test.ts

@@ -451,6 +451,7 @@ describe("getSchedule", () => {
         endTime: `${plus2DateString}T18:29:59.999Z`,
         timeZone: Timezones["+5:30"],
       });
+
       expect(scheduleForEventWith30Length).toHaveTimeSlots(
         [
           `04:00:00.000Z`,
@@ -484,8 +485,9 @@ describe("getSchedule", () => {
         timeZone: Timezones["+5:30"],
       });
       // `slotInterval` takes precedence over `length`
+      // 4:30 is utc so it is 10:00 in IST
       expect(scheduleForEventWith30minsLengthAndSlotInterval2hrs).toHaveTimeSlots(
-        [`04:00:00.000Z`, `06:00:00.000Z`, `08:00:00.000Z`, `10:00:00.000Z`, `12:00:00.000Z`],
+        [`04:30:00.000Z`, `06:30:00.000Z`, `08:30:00.000Z`, `10:30:00.000Z`, `12:30:00.000Z`],
         {
           dateString: plus2DateString,
         }

packages/lib/slots.test.ts

@@ -280,4 +280,23 @@ describe("Tests the slot logic", () => {
 
     expect(slots[0].time.format()).toBe("2023-07-13T22:45:00+02:00");
   });
+
+  it("tests slots for half hour timezones", async () => {
+    const slots = getSlots({
+      inviteeDate: dayjs.tz("2023-07-13T00:00:00.000+05:30", "Asia/Kolkata"),
+      frequency: 60,
+      minimumBookingNotice: 0,
+      eventLength: 60,
+      organizerTimeZone: "Asia/Kolkata",
+      dateRanges: [
+        {
+          start: dayjs.tz("2023-07-13T07:30:00.000", "Asia/Kolkata"),
+          end: dayjs.tz("2023-07-13T09:30:00.000", "Asia/Kolkata"),
+        },
+      ],
+    });
+
+    expect(slots).toHaveLength(1);
+    expect(slots[0].time.format()).toBe("2023-07-13T08:00:00+05:30");
+  });
 });

packages/lib/slots.ts

@@ -161,6 +161,7 @@ function buildSlotsWithDateRanges({
   eventLength = minimumOfOne(eventLength);
   offsetStart = offsetStart ? minimumOfOne(offsetStart) : 0;
   const slots: { time: Dayjs; userIds?: number[] }[] = [];
+
   dateRanges.forEach((range) => {
     const startTimeWithMinNotice = dayjs.utc().add(minimumBookingNotice, "minute");
 
@@ -178,7 +179,7 @@ function buildSlotsWithDateRanges({
     }
 
     slotStartTime =
-      slotStartTime.utc().minute() % interval !== 0
+      slotStartTime.minute() % interval !== 0
         ? slotStartTime.startOf("hour").add(Math.ceil(slotStartTime.minute() / interval) * interval, "minute")
         : slotStartTime;