diff --git a/packages/trpc/server/routers/viewer/slots/types.ts b/packages/trpc/server/routers/viewer/slots/types.ts
index d9a78e7ede..78afb85cd9 100644
--- a/packages/trpc/server/routers/viewer/slots/types.ts
+++ b/packages/trpc/server/routers/viewer/slots/types.ts
@@ -3,40 +3,45 @@ import { z } from "zod";
 
 import { timeZoneSchema } from "@calcom/lib/dayjs/timeZone.schema";
 
-export const getScheduleSchema = z
-  .object({
-    // startTime ISOString
-    startTime: z.string(),
-    // endTime ISOString
-    endTime: z.string(),
-    // Event type ID
-    eventTypeId: z.coerce.number().int().optional(),
-    // Event type slug
-    eventTypeSlug: z.string().optional(),
-    // invitee timezone
-    timeZone: timeZoneSchema.optional(),
-    // or list of users (for dynamic events)
-    usernameList: z.array(z.string()).min(1).optional(),
-    debug: z.boolean().optional(),
-    // to handle event types with multiple duration options
-    duration: z
-      .string()
-      .optional()
-      .transform((val) => val && parseInt(val)),
-    rescheduleUid: z.string().nullish(),
-    // whether to do team event or user event
-    isTeamEvent: z.boolean().optional().default(false),
-    orgSlug: z.string().nullish(),
-    teamMemberEmail: z.string().nullish(),
-    routedTeamMemberIds: z.array(z.number()).nullish(),
-    skipContactOwner: z.boolean().nullish(),
-    _enableTroubleshooter: z.boolean().optional(),
-    _bypassCalendarBusyTimes: z.boolean().optional(),
-    _shouldServeCache: z.boolean().optional(),
-    routingFormResponseId: z.number().optional(),
-    queuedFormResponseId: z.string().nullish(),
-    email: z.string().nullish(),
-  })
+const isValidDateString = (val: string) => !isNaN(Date.parse(val));
+
+export const getScheduleSchemaObject = z.object({
+  startTime: z.string().refine(isValidDateString, {
+    message: "startTime must be a valid date string",
+  }),
+  endTime: z.string().refine(isValidDateString, {
+    message: "endTime must be a valid date string",
+  }),
+  // Event type ID
+  eventTypeId: z.coerce.number().int().optional(),
+  // Event type slug
+  eventTypeSlug: z.string().optional(),
+  // invitee timezone
+  timeZone: timeZoneSchema.optional(),
+  // or list of users (for dynamic events)
+  usernameList: z.array(z.string()).min(1).optional(),
+  debug: z.boolean().optional(),
+  // to handle event types with multiple duration options
+  duration: z
+    .string()
+    .optional()
+    .transform((val) => val && parseInt(val)),
+  rescheduleUid: z.string().nullish(),
+  // whether to do team event or user event
+  isTeamEvent: z.boolean().optional().default(false),
+  orgSlug: z.string().nullish(),
+  teamMemberEmail: z.string().nullish(),
+  routedTeamMemberIds: z.array(z.number()).nullish(),
+  skipContactOwner: z.boolean().nullish(),
+  _enableTroubleshooter: z.boolean().optional(),
+  _bypassCalendarBusyTimes: z.boolean().optional(),
+  _shouldServeCache: z.boolean().optional(),
+  routingFormResponseId: z.number().optional(),
+  queuedFormResponseId: z.string().nullish(),
+  email: z.string().nullish(),
+});
+
+export const getScheduleSchema = getScheduleSchemaObject
   .transform((val) => {
     // Need this so we can pass a single username in the query string form public API
     if (val.usernameList) {
@@ -50,7 +55,11 @@ export const getScheduleSchema = z
   .refine(
     (data) => !!data.eventTypeId || (!!data.usernameList && !!data.eventTypeSlug),
     "You need to either pass an eventTypeId OR an usernameList/eventTypeSlug combination"
-  );
+  )
+  .refine(({ startTime, endTime }) => new Date(endTime).getTime() > new Date(startTime).getTime(), {
+    message: "endTime must be after startTime",
+    path: ["endTime"],
+  });
 
 export const reserveSlotSchema = z
   .object({
@@ -82,7 +91,7 @@ export interface ContextForGetSchedule extends Record<string, unknown> {
   req?: (IncomingMessage & { cookies: Partial<{ [key: string]: string }> }) | undefined;
 }
 
-export type TGetScheduleInputSchema = z.infer<typeof getScheduleSchema>;
+export type TGetScheduleInputSchema = z.infer<typeof getScheduleSchemaObject>;
 export const ZGetScheduleInputSchema = getScheduleSchema;
 
 export type GetScheduleOptions = {
diff --git a/packages/trpc/server/routers/viewer/slots/util.ts b/packages/trpc/server/routers/viewer/slots/util.ts
index 2489a84e0a..e14b6771b2 100644
--- a/packages/trpc/server/routers/viewer/slots/util.ts
+++ b/packages/trpc/server/routers/viewer/slots/util.ts
@@ -186,10 +186,8 @@ export class AvailableSlotsService {
     const { currentOrgDomain, isValidOrgDomain } = organizationDetails;
     // For dynamic booking, we need to get and update user credentials, schedule and availability in the eventTypeObject as they're required in the new availability logic
     if (!input.eventTypeSlug) {
-      throw new TRPCError({
-        message: "eventTypeSlug is required for dynamic booking",
-        code: "BAD_REQUEST",
-      });
+      // never happens as it's guarded by our Zod Schema refine, but for clear type safety we throw an Error if the eventTypeSlug isn't given.
+      throw new Error("Event type slug is required in dynamic booking.");
     }
     const dynamicEventType = getDefaultEvent(input.eventTypeSlug);
 
@@ -634,19 +632,6 @@ export class AvailableSlotsService {
 
       limitManager.mergeBusyTimes(globalLimitManager);
 
-      const bookingLimitsParams = {
-        bookings: userBusyTimes,
-        bookingLimits,
-        dateFrom,
-        dateTo,
-        limitManager,
-        rescheduleUid,
-        teamId,
-        user,
-        includeManagedEvents,
-        timeZone,
-      };
-
       for (const key of descendingLimitKeys) {
         const limit = bookingLimits?.[key];
         if (!limit) continue;
@@ -1011,10 +996,6 @@ export class AvailableSlotsService {
     );
     const endTime =
       input.timeZone === "Etc/GMT" ? dayjs.utc(input.endTime) : dayjs(input.endTime).utc().tz(input.timeZone);
-
-    if (!startTime.isValid() || !endTime.isValid()) {
-      throw new TRPCError({ message: "Invalid time range given.", code: "BAD_REQUEST" });
-    }
     // when an empty array is given we should prefer to have it handled as if this wasn't given at all
     // we don't want to return no availability in this case.
     const routedTeamMemberIds = input.routedTeamMemberIds ?? [];
@@ -1164,11 +1145,9 @@ export class AvailableSlotsService {
         scheduleId: eventType.restrictionScheduleId,
       });
       if (restrictionSchedule) {
+        // runtime error preventing misconfiguration when restrictionSchedule timeZone must be used.
         if (!eventType.useBookerTimezone && !restrictionSchedule.timeZone) {
-          throw new TRPCError({
-            message: "No timezone is set for the restricted schedule",
-            code: "BAD_REQUEST",
-          });
+          throw new Error("No timezone is set for the restricted schedule");
         }
 
         const restrictionTimezone = eventType.useBookerTimezone