diff --git a/components/book/dateSelect.tsx b/components/book/dateSelect.tsx
index e31311b..bb48879 100644
--- a/components/book/dateSelect.tsx
+++ b/components/book/dateSelect.tsx
@@ -3,19 +3,20 @@ import { BookContext } from '../../context/book'
 import InputWrapper from '../inputWrapper'
 import Input from '../input'
 import Calendar from '../calendar'
+import { dateFormatBackend } from '../../helpers/date'
 
 export default function DateSelect() {
   const { onChangeEvent, onChange, state } = useContext(BookContext)
   const { startDate, endDate } = state.formData
 
-  const today = new Date().toISOString().substring(0, 10)
+  const today = dateFormatBackend(new Date())
 
   return (
     <>
       <InputWrapper label="Datum" required>
         <Calendar
-          start={startDate}
-          end={endDate}
+          start={dateFormatBackend(startDate)}
+          end={dateFormatBackend(endDate)}
           onChange={onChange}
           className="my-6 max-w-lg"
         />
@@ -27,7 +28,7 @@ export default function DateSelect() {
             type="date"
             className=""
             name="startDate"
-            value={startDate || ''}
+            value={dateFormatBackend(startDate) || ''}
             onChange={onChangeEvent}
             min={today}
             required
@@ -40,10 +41,10 @@ export default function DateSelect() {
             type="date"
             className=""
             name="endDate"
-            value={endDate || ''}
+            value={dateFormatBackend(endDate) || ''}
             placeholder="Von"
             onChange={onChangeEvent}
-            min={startDate || today}
+            min={dateFormatBackend(startDate) || today}
           />
         </div>
       </div>
diff --git a/components/calendar.tsx b/components/calendar.tsx
index 49c808b..a78fd90 100644
--- a/components/calendar.tsx
+++ b/components/calendar.tsx
@@ -122,15 +122,15 @@ export default function MyCalendar({
 
             // when startDate missing or both are already set
             if (!startDate || (!!startDate && !!endDate)) {
-              onChange({ startDate: dateFormatBackend(date), endDate: null })
+              onChange({ startDate: date, endDate: null })
               return
             }
 
             // when startDate set, but end missing
             if (isAfter(date, startDate)) {
-              onChange({ endDate: dateFormatBackend(date) })
+              onChange({ endDate: date })
             } else {
-              onChange({ startDate: dateFormatBackend(date), endDate: start })
+              onChange({ startDate: date, endDate: date })
             }
           }}
           tileClassName={tileClassName}
diff --git a/context/book.tsx b/context/book.tsx
index 34b779c..b06d5d8 100644
--- a/context/book.tsx
+++ b/context/book.tsx
@@ -5,7 +5,7 @@ import { clearBookingData, loadBookingData } from '../helpers/storage'
 import { createBooking } from '../helpers/booking'
 import { Booking } from '../db/booking'
 
-export type BookFormData = Omit<Booking, 'uuid' | 'calendarEventId'>
+export type BookFormData = Omit<Booking, 'uuid' | 'calendarEventId' | 'start' | 'end'>
 
 type BookingProviderState = {
   postData?: boolean
@@ -103,8 +103,8 @@ const initialState: BookingProviderState = {
   postDataError: null,
   postDataSuccess: null,
   formData: {
-    startDate: '',
-    endDate: '',
+    startDate: null,
+    endDate: null,
     purpose: '',
     org: '',
     destination: '',
diff --git a/db/booking.ts b/db/booking.ts
index 18185ac..4555453 100644
--- a/db/booking.ts
+++ b/db/booking.ts
@@ -16,8 +16,10 @@ export type Booking = {
   zip: string
   city: string
   bill?: Bill
-  startDate: string
-  endDate: string
+  start: string
+  startDate: Date
+  endDate: Date
+  end: string
   status?: BOOKING_STATUS
   purpose?: string
   org?: string
@@ -56,26 +58,10 @@ const BookingSchema = new mongoose.Schema<BookingDocument>(
     startDate: {
       type: Date,
       required: true,
-      get: dateFormatBackend,
-      validate: {
-        validator: function (v: Date): boolean {
-          return v >= nowInTz()
-        },
-        message: (props: { value: Date }): string =>
-          `${props.value} is in the past`,
-      },
     },
     endDate: {
       type: Date,
       required: false,
-      get: dateFormatBackend,
-      validate: {
-        validator: function (v: Date): boolean {
-          return v >= nowInTz()
-        },
-        message: (props: { value: Date }): string =>
-          `${props.value} is in the past`,
-      },
     },
     days: {
       type: [String],
@@ -100,7 +86,7 @@ const BookingSchema = new mongoose.Schema<BookingDocument>(
       type: String,
       enum: Object.values(BOOKING_STATUS),
       required: true,
-      default: 'requested',
+      default: BOOKING_STATUS.REQUESTED,
     },
     purpose: { type: String, required: false },
     org: { type: String, required: false },
@@ -114,6 +100,16 @@ const BookingSchema = new mongoose.Schema<BookingDocument>(
   }
 )
 
+BookingSchema.virtual('start').get(function (): string {
+  const booking = this as BookingDocument
+  return dateFormatBackend(booking.startDate)
+})
+
+BookingSchema.virtual('end').get(function (): string {
+  const booking = this as BookingDocument
+  return dateFormatBackend(booking.endDate)
+})
+
 BookingSchema.pre('validate', function (next: () => void): void {
   const booking = this as BookingDocument
   booking.days = getDays({
diff --git a/db/index.ts b/db/index.ts
index c3563a2..e5fab30 100644
--- a/db/index.ts
+++ b/db/index.ts
@@ -7,18 +7,12 @@ let connectedPromise: Promise<mongoose.Mongoose>
 
 export const MONGO_URI = process.env.MONGO_URI
 
-export const MONGODB_OPTIONS = {
-  useCreateIndex: true,
-  useNewUrlParser: true,
-  useUnifiedTopology: true,
-}
-
 export function connect(): Promise<mongoose.Mongoose> {
   if (connectedPromise) {
     return connectedPromise
   }
 
-  connectedPromise = mongoose.connect(process.env.MONGO_URI, MONGODB_OPTIONS)
+  connectedPromise = mongoose.connect(process.env.MONGO_URI)
 
   return connectedPromise
 }
diff --git a/lib/getServerSideProps.ts b/lib/getServerSideProps.ts
index 12fec42..5fdfd7a 100644
--- a/lib/getServerSideProps.ts
+++ b/lib/getServerSideProps.ts
@@ -47,7 +47,7 @@ export const getServerSideBooking = async (
     return { props: { booking: null } }
   }
 
-  await booking.populate('bill').execPopulate()
+  await booking.populate('bill')
 
   // TODO: hack, not sure why _id is not serilizable
   const bookingJSON = JSON.parse(JSON.stringify(booking.toJSON())) as object
diff --git a/lib/googlecalendar.ts b/lib/googlecalendar.ts
index 7b67182..2bf34c3 100644
--- a/lib/googlecalendar.ts
+++ b/lib/googlecalendar.ts
@@ -50,10 +50,10 @@ export async function createCalendarEvent(booking: Booking): Promise<Booking> {
     requestBody: {
       summary: getSummary(booking),
       // description,
-      start: { date: booking.startDate },
-      end: { date: booking.endDate },
+      start: { date: booking.start },
+      end: { date: booking.end },
     },
-  })
+  }, {})
 
   booking.calendarEventId = response.data.id
 
diff --git a/pages/admin/bookings/[uuid]/index.tsx b/pages/admin/bookings/[uuid]/index.tsx
index 5ac5dce..62e8c1f 100644
--- a/pages/admin/bookings/[uuid]/index.tsx
+++ b/pages/admin/bookings/[uuid]/index.tsx
@@ -38,7 +38,7 @@ function ShowBookingAdmin({ booking: bookingProp }: { booking: Booking }) {
   return (
     <Layout>
       <h2 className="text-3xl">Buchung {booking.uuid}</h2>
-      <Calendar start={booking.startDate} end={booking.endDate} />
+      <Calendar start={booking.start} end={booking.end} />
       <div>
         <strong>Buchungszeitraum:</strong> {daysFormatFrontend(booking.days)}
       </div>
diff --git a/pages/api/auth/[...nextauth].ts b/pages/api/auth/[...nextauth].ts
index 61089a9..5059177 100644
--- a/pages/api/auth/[...nextauth].ts
+++ b/pages/api/auth/[...nextauth].ts
@@ -3,14 +3,14 @@ import NextAuth from 'next-auth'
 import EmailProvider from 'next-auth/providers/email'
 
 import { MongoDBAdapter } from '@next-auth/mongodb-adapter'
-import { MONGO_URI, MONGODB_OPTIONS } from '../../../db'
+import { MONGO_URI } from '../../../db'
 import { MongoClient } from 'mongodb'
 
 let client: MongoClient
 
 async function getMongoClient() {
   if (!client) {
-    client = new MongoClient(MONGO_URI, MONGODB_OPTIONS)
+    client = new MongoClient(MONGO_URI)
     await client.connect()
   }
 
diff --git a/pages/api/bookings/[uuid]/bill.ts b/pages/api/bookings/[uuid]/bill.ts
index 3ce5a0a..be954c2 100644
--- a/pages/api/bookings/[uuid]/bill.ts
+++ b/pages/api/bookings/[uuid]/bill.ts
@@ -1,7 +1,11 @@
+import { NextApiRequest, NextApiResponse } from 'next'
 import { Bill } from '../../../../db/bill'
 import { createBill, patchBill } from '../../../../db/index'
 
-export default async function billHandler(req, res): Promise<void> {
+export default async function billHandler(
+  req: NextApiRequest,
+  res: NextApiResponse
+  ): Promise<void> {
   const {
     method,
     query: { uuid: uuids },