diff --git a/app/lib/actions/locationActions.ts b/app/lib/actions/locationActions.ts
index dc7192b..cd704c2 100644
--- a/app/lib/actions/locationActions.ts
+++ b/app/lib/actions/locationActions.ts
@@ -4,7 +4,7 @@ import { z } from 'zod';
 import { revalidatePath } from 'next/cache';
 import { redirect } from 'next/navigation';
 import clientPromise, { getDbClient } from '../dbClient';
-import { BillingLocation } from '../db-types';
+import { BillingLocation, YearMonth } from '../db-types';
 import { ObjectId } from 'mongodb';
 import { auth, withUser } from '@/app/lib/auth';
 import { AuthenticatedUser } from '../types/next-auth';
@@ -33,7 +33,7 @@ const UpdateLocation = FormSchema.omit({ _id: true });
  * @param formData form data
  * @returns 
  */
-export const updateOrAddLocation = withUser(async (user:AuthenticatedUser, locationId?: string, year?: string, month?: string, prevState:State, formData: FormData) => {
+export const updateOrAddLocation = withUser(async (user:AuthenticatedUser, locationId?: string, yearMonth?: YearMonth, prevState:State, formData: FormData) => {
 
     const validatedFields = UpdateLocation.safeParse({
         locationName: formData.get('locationName'),
@@ -70,15 +70,14 @@ export const updateOrAddLocation = withUser(async (user:AuthenticatedUser, locat
                     notes: locationNotes,
                 }
             });
-    } else if(year && month) {
+    } else if(yearMonth) {
         await dbClient.collection<BillingLocation>("lokacije").insertOne({
             _id: (new ObjectId()).toHexString(),
             userId,
             userEmail,
             name: locationName,
             notes: locationNotes,
-            year: parseInt(year), // ToDo: get the current year and month
-            month: parseInt(month), // ToDo: get the current year and month
+            yearMonth: yearMonth,
             bills: [],
         });
     }
@@ -99,7 +98,7 @@ export const fetchAllLocations = withUser(async (user:AuthenticatedUser, pageIx:
     // fetch `pageSize` locations for the given page index
     const locations = await dbClient.collection<BillingLocation>("lokacije")
         .find({ userId })
-        .sort({ year: -1, month: -1, name: 1 })
+        .sort({ yearMonth: -1, name: 1 })
         .skip(pageIx * pageSize)
         .limit(pageSize)
         .toArray();
diff --git a/app/lib/actions/monthActions.ts b/app/lib/actions/monthActions.ts
index 7689d62..b6c083a 100644
--- a/app/lib/actions/monthActions.ts
+++ b/app/lib/actions/monthActions.ts
@@ -4,7 +4,7 @@ import { revalidatePath } from 'next/cache';
 import { redirect } from 'next/navigation';
 import clientPromise, { getDbClient } from '../dbClient';
 import { ObjectId } from 'mongodb';
-import { BillingLocation } from '../db-types';
+import { BillingLocation, YearMonth } from '../db-types';
 import { AuthenticatedUser } from '../types/next-auth';
 import { withUser } from '../auth';
 
@@ -16,14 +16,12 @@ import { withUser } from '../auth';
  * @param formData form data
  * @returns 
  */
-export const addMonth = withUser(async (user:AuthenticatedUser, yearString: string, monthString: string) => {
+export const addMonth = withUser(async (user:AuthenticatedUser, { year, month }: YearMonth) => {
     const { id: userId } = user;
 
     // update the bill in the mongodb
     const dbClient = await getDbClient();
 
-    const year = parseInt(yearString);
-    const month = parseInt(monthString);
 
     const prevYear = month === 1 ? year - 1 : year;
     const prevMonth = month === 1 ? 12 : month - 1;
@@ -31,8 +29,10 @@ export const addMonth = withUser(async (user:AuthenticatedUser, yearString: stri
     // find all locations for the previous month
     const prevMonthLocations = await dbClient.collection<BillingLocation>("lokacije").find({
         userId, // make sure that the locations belongs to the user
-        year: prevYear,
-        month: prevMonth,
+        yearMonth: {
+            year: prevYear,
+            month: prevMonth,
+        }
     });
 
     const newMonthLocationsCursor = prevMonthLocations.map((prevLocation) => {
@@ -41,8 +41,10 @@ export const addMonth = withUser(async (user:AuthenticatedUser, yearString: stri
             ...prevLocation,
             // assign a new ID
             _id: (new ObjectId()).toHexString(),
-            year: year,
-            month: month,
+            yearMonth: {
+                year: year,
+                month: month,
+            },
             // copy bill array, but set all bills to unpaid and remove attachments and notes
             bills: prevLocation.bills.map((bill) => {
                 return {
diff --git a/app/lib/db-types.ts b/app/lib/db-types.ts
index d7bdc20..a116986 100644
--- a/app/lib/db-types.ts
+++ b/app/lib/db-types.ts
@@ -9,6 +9,11 @@ export interface BillAttachment {
     fileContentsBase64: string;
 };
 
+export interface YearMonth {
+    year: number;
+    month: number;
+};
+
 /** bill object in the form returned by MongoDB */
 export interface BillingLocation {
     _id: string;
@@ -18,10 +23,8 @@ export interface BillingLocation {
     userEmail?: string | null;
     /** name of the location */
     name: string;
-    /** billing period year */
-    year: number;
-    /** billing period month */
-    month: number;
+    /** billing period year and month */
+    yearMonth: YearMonth;
     /** array of bills */
     bills: Bill[];
     /** (optional) notes */
diff --git a/app/lib/format.ts b/app/lib/format.ts
index cd0ea6a..def9c9d 100644
--- a/app/lib/format.ts
+++ b/app/lib/format.ts
@@ -1,4 +1,12 @@
+import { YearMonth } from "./db-types";
 
-export const formatYearMonth = (year: number, month:number): string => {
+export const formatYearMonth = ({ year, month }: YearMonth): string => {
   return `${year}-${month<10?"0":""}${month}`;
 }
+
+export const parseYearMonth = (yearMonthString: string): YearMonth => {
+
+  const [year, month] = yearMonthString.split("-").map((s) => parseInt(s, 10));
+
+  return({ year, month } as YearMonth);
+}
diff --git a/app/location/[id]/add/page.tsx b/app/location/[id]/add/page.tsx
index 26036aa..24abc7a 100644
--- a/app/location/[id]/add/page.tsx
+++ b/app/location/[id]/add/page.tsx
@@ -1,7 +1,6 @@
+import { parseYearMonth } from '@/app/lib/format';
 import { LocationEditForm } from '@/app/ui/LocationEditForm';
 
 export default async function Page({ params:{ id } }: { params: { id:string } }) {
-
-    const [year, month] = id.split("-");
-    return (<LocationEditForm year={year} month={month} />);
+    return (<LocationEditForm yearMonth={ parseYearMonth(id) } />);
 }
\ No newline at end of file
diff --git a/app/page.tsx b/app/page.tsx
index 91f5f7e..3f90a56 100644
--- a/app/page.tsx
+++ b/app/page.tsx
@@ -7,18 +7,21 @@ import { isAuthErrorMessage } from '@/app/lib/auth';
 import { fetchAllLocations } from './lib/actions/locationActions';
 import { formatCurrency } from './lib/formatStrings';
 import { fetchAvailableYears } from './lib/actions/monthActions';
+import { YearMonth } from './lib/db-types';
+import { formatYearMonth } from './lib/format';
 
-const getNextYearMonth = (year:number, month:number) => {
+const getNextYearMonth = (yearMonth:YearMonth) => {
+  const {year, month} = yearMonth;
   return({
-    year: month<12 ? year+1 : year,
-    month: month<12 ? month+1 : 1
-  });
+    year: month===12 ? year+1 : year,
+    month: month===12 ? 1 : month+1
+  } as YearMonth);
 }
 
 export const Page = async () => {
 
  const locations = await fetchAllLocations();
- const availableYearMonths = await fetchAvailableYears();
+ const availableYears = await fetchAvailableYears();
 
  if(isAuthErrorMessage(locations)) {
   return (
@@ -30,13 +33,15 @@ export const Page = async () => {
   // if the database is in it's initial state, show the add location button for the current month
   if(locations.length === 0) {
     
-    const currentYear = new Date().getFullYear();
-    const currentMonth = new Date().getMonth() + 1; 
+    const currentYearMonth:YearMonth = {
+      year: new Date().getFullYear(),
+      month: new Date().getMonth() + 1
+    };
     
     return (
       <main className="flex min-h-screen flex-col p-6 bg-base-300">
-        <MonthTitle year={currentYear} month={currentMonth} />
-        <AddLocationButton year={currentYear} month={currentMonth} />
+        <MonthTitle yearMonth={currentYearMonth} />
+        <AddLocationButton yearMonth={currentYearMonth} />
         <PageFooter />
       </main>
     );
@@ -46,13 +51,17 @@ export const Page = async () => {
 
  return (
     <main className="flex min-h-screen flex-col p-6 bg-base-300">
-        <AddMonthButton {...getNextYearMonth(locations[0].year, locations[0].month)} />
+        <AddMonthButton yearMonth={getNextYearMonth(locations[0].yearMonth)} />
         {
           locations.map((location, ix, array) => {
 
-            const isFirstLocationInMonth = ix === 0 || location.year !== array[ix-1].year || location.month !== array[ix-1].month;
-            const isLastLocationInMonth = location.year !== array[ix+1]?.year || location.month !== array[ix+1]?.month;
-            const isLastLocationOfFirstMonth = isLastLocationInMonth && location.year === array[0].year && location.month === array[0].month;
+            const { year, month } = location.yearMonth
+            const { year: prevYear, month: prevMonth } = array[ix-1]?.yearMonth ?? { year: undefined, month: undefined };
+            const { year: nextYear, month: nextMonth } = array[ix+1]?.yearMonth ?? { year: undefined, month: undefined };
+
+            const isFirstLocationInMonth = ix === 0 || year !== prevYear || month !== prevMonth;
+            const isLastLocationInMonth = year !== nextYear || month !== nextMonth;
+            const isLastLocationOfFirstMonth = isLastLocationInMonth && year === array[0].yearMonth.year && month === array[0].yearMonth.month
 
             if(isFirstLocationInMonth) {
               monthlyExpense = 0;
@@ -65,13 +74,13 @@ export const Page = async () => {
                 {
                   // show month title above the first LocationCard in the month
                   isFirstLocationInMonth ?
-                    <MonthTitle key={`${location.year}-${location.month}`} year={location.year} month={location.month} /> : null
+                    <MonthTitle key={`${year}-${month}`} yearMonth={location.yearMonth} /> : null
                 }
                 <LocationCard key={`${location._id}`} location={location} />
                 {
                   // show AddLocationButton as a last item in the firts month
                   isLastLocationOfFirstMonth ?
-                    <AddLocationButton key={`add-loc-${location.year}-${location.month}`} year={location.year} month={location.month} /> : null
+                    <AddLocationButton key={`add-loc-${formatYearMonth(location.yearMonth)}`} yearMonth={location.yearMonth} /> : null
                 }
                 {
                   isLastLocationInMonth && monthlyExpense>0 ?
@@ -88,7 +97,7 @@ export const Page = async () => {
           })
         }
         <PageFooter />
-        { availableYearMonths.map(ym => <p key={`year-month-${ym}`}>{ym}</p>) }
+        { availableYears.map(ym => <p key={`year-month-${ym}`}>{ym}</p>) }
     </main>
   );
 }
diff --git a/app/ui/AddLocationButton.tsx b/app/ui/AddLocationButton.tsx
index 7191385..9dbd30c 100644
--- a/app/ui/AddLocationButton.tsx
+++ b/app/ui/AddLocationButton.tsx
@@ -1,16 +1,16 @@
 import { PlusCircleIcon } from "@heroicons/react/24/outline";
+import { YearMonth } from "../lib/db-types";
+import { formatYearMonth } from "../lib/format";
 
 
 export interface AddLocationButtonProps {
-    /** year at which the new billing location should be addes */
-    year: number
-    /** month at which the new billing location should be addes */
-    month: number
+    /** year and month at which the new billing location should be addes */
+    yearMonth: YearMonth
 }
 
-export const AddLocationButton:React.FC<AddLocationButtonProps> = ({year,month}) =>
+export const AddLocationButton:React.FC<AddLocationButtonProps> = ({yearMonth}) =>
 <div className="card card-compact card-bordered max-w-[36em] bg-base-100 shadow-s my-1">
-    <a href={`/location/${year}-${month<10?"0":""}${month}/add`} className="card-body tooltip self-center" data-tip="Add a new billing location">
+    <a href={`/location/${ formatYearMonth(yearMonth) }/add`} className="card-body tooltip self-center" data-tip="Add a new billing location">
         <span className='grid self-center' data-tip="Add a new billing location">
             <PlusCircleIcon className="h-[1em] w-[1em] cursor-pointer text-4xl" />
         </span>
diff --git a/app/ui/AddMonthButton.tsx b/app/ui/AddMonthButton.tsx
index 535b9bc..7f7b08a 100644
--- a/app/ui/AddMonthButton.tsx
+++ b/app/ui/AddMonthButton.tsx
@@ -1,12 +1,13 @@
 import { PlusCircleIcon } from "@heroicons/react/24/outline";
 import React from "react";
+import { formatYearMonth } from "../lib/format";
+import { YearMonth } from "../lib/db-types";
 
 export interface AddMonthButtonProps {
-    year: number;
-    month: number;
+    yearMonth: YearMonth;
 }
 
-export const AddMonthButton:React.FC<AddMonthButtonProps> = ({ year, month }) =>
-<a href={`/year-month/${year}-${month<10?"0":""}${month}/add`} className='grid self-center tooltip' data-tip="Dodaj novi mjesec">
+export const AddMonthButton:React.FC<AddMonthButtonProps> = ({ yearMonth }) =>
+<a href={`/year-month/${formatYearMonth(yearMonth)}/add`} className='grid self-center tooltip' data-tip="Dodaj novi mjesec">
     <PlusCircleIcon className="h-[1em] w-[1em] cursor-pointer text-4xl" />
 </a>
diff --git a/app/ui/LocationCard.tsx b/app/ui/LocationCard.tsx
index d51eb1f..addc8ca 100644
--- a/app/ui/LocationCard.tsx
+++ b/app/ui/LocationCard.tsx
@@ -11,7 +11,7 @@ export interface LocationCardProps {
     location: BillingLocation
 }
 
-export const LocationCard:FC<LocationCardProps> = ({location: { _id, name, year, month, bills }}) => {
+export const LocationCard:FC<LocationCardProps> = ({location: { _id, name, yearMonth, bills }}) => {
 
     // sum all the billAmounts
     const monthlyExpense = bills.reduce((acc, bill) => acc + (bill.payedAmount ?? 0), 0);
@@ -22,7 +22,7 @@ export const LocationCard:FC<LocationCardProps> = ({location: { _id, name, year,
                 <a href={`/location/${_id}/edit`} className="card-subtitle tooltip" data-tip="Edit Location">
                     <Cog8ToothIcon className="h-[1em] w-[1em] absolute cursor-pointer top-3 right-3 text-2xl" />
                 </a>
-                <h2 className="card-title">{formatYearMonth(year, month)} {name}</h2>
+                <h2 className="card-title">{formatYearMonth(yearMonth)} {name}</h2>
                 <div className="card-actions">
                     {
                         bills.map(bill => <BillBadge key={`${bill._id}`} locationId={_id} bill={bill} />)
diff --git a/app/ui/LocationEditForm.tsx b/app/ui/LocationEditForm.tsx
index 64769fa..5fd3c28 100644
--- a/app/ui/LocationEditForm.tsx
+++ b/app/ui/LocationEditForm.tsx
@@ -2,7 +2,7 @@
 
 import { TrashIcon } from "@heroicons/react/24/outline";
 import { FC } from "react";
-import { BillingLocation } from "../lib/db-types";
+import { BillingLocation, YearMonth } from "../lib/db-types";
 import { updateOrAddLocation } from "../lib/actions/locationActions";
 import { useFormState } from "react-dom";
 import { gotoHome } from "../lib/actions/billActions";
@@ -10,16 +10,14 @@ import { gotoHome } from "../lib/actions/billActions";
 export interface LocationEditFormProps {
     /** location which should be edited */
     location?: BillingLocation,
-    /** year at a new billing location should be assigned */
-    year?: string
-    /** month at a new billing location should be assigned */
-    month?: string
+    /** year adn month at a new billing location should be assigned */
+    yearMonth?: YearMonth   
 }
 
-export const LocationEditForm:FC<LocationEditFormProps> = ({ location, year, month }) =>
+export const LocationEditForm:FC<LocationEditFormProps> = ({ location, yearMonth }) =>
 {
     const initialState = { message: null, errors: {} };
-    const handleAction = updateOrAddLocation.bind(null, location?._id, year, month);
+    const handleAction = updateOrAddLocation.bind(null, location?._id, yearMonth);
     const [ state, dispatch ] = useFormState(handleAction, initialState);
 
     // redirect to the main page
diff --git a/app/ui/MonthTitle.tsx b/app/ui/MonthTitle.tsx
index f02940f..ee46344 100644
--- a/app/ui/MonthTitle.tsx
+++ b/app/ui/MonthTitle.tsx
@@ -1,10 +1,10 @@
 import { FC } from "react";
 import { formatYearMonth } from "../lib/format";
+import { YearMonth } from "../lib/db-types";
 
 export interface MonthTitleProps {
-    year: number;
-    month: number;
+    yearMonth: YearMonth
 }
 
-export const MonthTitle:FC<MonthTitleProps> = ({year, month}) =>
-<div className="divider text-2xl">{`${formatYearMonth(year, month)}`}</div>
\ No newline at end of file
+export const MonthTitle:FC<MonthTitleProps> = ({ yearMonth }) =>
+<div className="divider text-2xl">{`${formatYearMonth(yearMonth)}`}</div>
\ No newline at end of file
diff --git a/app/year-month/[id]/add/page.tsx b/app/year-month/[id]/add/page.tsx
index ed28252..f56be44 100644
--- a/app/year-month/[id]/add/page.tsx
+++ b/app/year-month/[id]/add/page.tsx
@@ -1,12 +1,11 @@
 import { addMonth } from '@/app/lib/actions/monthActions';
+import { parseYearMonth } from '@/app/lib/format';
 import { revalidatePath } from 'next/cache';
 import { redirect } from 'next/navigation';
 
 export default async function Page({ params:{ id } }: { params: { id:string } }) {
 
-    const [year, month] = id.split("-");
-
-    await addMonth(year, month);
+    await addMonth(parseYearMonth(id));
 
     revalidatePath('/');
     redirect(`/`);