diff --git a/frontend/components/Project/useProjectMetrics.ts b/frontend/components/Project/useProjectMetrics.ts
index 8a03101..e9aba33 100644
--- a/frontend/components/Project/useProjectMetrics.ts
+++ b/frontend/components/Project/useProjectMetrics.ts
@@ -7,7 +7,7 @@ import {
     isTaskPlanned,
     isTaskWaiting,
 } from '../../constants/taskStatus';
-import { parseDateString, getTodayDateString } from '../../utils/dateUtils';
+import { parseDateString, getTodayDateString, toLocalDateString } from '../../utils/dateUtils';
 
 // Check if task is in today's plan (has active status)
 const isTaskInTodayPlan = (task: Task): boolean =>
@@ -181,7 +181,7 @@ export const useProjectMetrics = (
         for (let i = days - 1; i >= 0; i--) {
             const d = new Date(today);
             d.setDate(today.getDate() - i);
-            const key = d.toISOString().split('T')[0];
+            const key = toLocalDateString(d);
             labels.push({
                 dateKey: key,
                 label: `${d.getMonth() + 1}/${d.getDate()}`,
@@ -193,7 +193,7 @@ export const useProjectMetrics = (
 
         tasks.forEach((task) => {
             if (!task.completed_at) return;
-            const key = new Date(task.completed_at).toISOString().split('T')[0];
+            const key = toLocalDateString(new Date(task.completed_at));
             if (counts[key] !== undefined) {
                 counts[key] += 1;
             }
@@ -213,7 +213,7 @@ export const useProjectMetrics = (
         for (let i = days - 1; i >= 0; i--) {
             const d = new Date(today);
             d.setDate(today.getDate() - i);
-            const key = d.toISOString().split('T')[0];
+            const key = toLocalDateString(d);
             labels.push({
                 dateKey: key,
                 label: `${d.getMonth() + 1}/${d.getDate()}`,
@@ -225,7 +225,7 @@ export const useProjectMetrics = (
 
         tasks.forEach((task) => {
             if (!task.created_at) return;
-            const key = new Date(task.created_at).toISOString().split('T')[0];
+            const key = toLocalDateString(new Date(task.created_at));
             if (counts[key] !== undefined) {
                 counts[key] += 1;
             }
@@ -245,7 +245,7 @@ export const useProjectMetrics = (
         for (let i = 0; i < days; i++) {
             const d = new Date(today);
             d.setDate(today.getDate() + i);
-            const key = d.toISOString().split('T')[0];
+            const key = toLocalDateString(d);
             labels.push({
                 dateKey: key,
                 label: `${d.getMonth() + 1}/${d.getDate()}`,
diff --git a/frontend/components/Task/TaskDetails/TaskRecurrenceCard.tsx b/frontend/components/Task/TaskDetails/TaskRecurrenceCard.tsx
index 2078397..d07ad0a 100644
--- a/frontend/components/Task/TaskDetails/TaskRecurrenceCard.tsx
+++ b/frontend/components/Task/TaskDetails/TaskRecurrenceCard.tsx
@@ -5,6 +5,7 @@ import TaskRecurrenceSection from '../TaskForm/TaskRecurrenceSection';
 import TaskRecurringInstanceInfo from './TaskRecurringInstanceInfo';
 import { Task, RecurrenceType } from '../../../entities/Task';
 import { TaskIteration } from '../../../utils/tasksService';
+import { getTodayDateString } from '../../../utils/dateUtils';
 
 interface TaskRecurrenceCardProps {
     task: Task;
@@ -48,7 +49,7 @@ const TaskRecurrenceCard: React.FC<TaskRecurrenceCardProps> = ({
 
     const formatDateWithDayName = (dateString: string) => {
         const date = new Date(dateString);
-        const today = new Date().toISOString().split('T')[0];
+        const today = getTodayDateString();
         const isToday = dateString === today;
 
         const dayName = date.toLocaleDateString(i18n.language, {
diff --git a/frontend/components/Task/TaskDueDate.tsx b/frontend/components/Task/TaskDueDate.tsx
index 1923a54..bb50240 100644
--- a/frontend/components/Task/TaskDueDate.tsx
+++ b/frontend/components/Task/TaskDueDate.tsx
@@ -1,6 +1,6 @@
 import React from 'react';
 import { useTranslation } from 'react-i18next';
-import { parseDateString } from '../../utils/dateUtils';
+import { parseDateString, getTodayDateString, getTomorrowDateString, getYesterdayDateString } from '../../utils/dateUtils';
 
 interface TaskDueDateProps {
     dueDate: string;
@@ -10,10 +10,8 @@ interface TaskDueDateProps {
 const TaskDueDate: React.FC<TaskDueDateProps> = ({ dueDate, className }) => {
     const { t } = useTranslation();
     const getDueDateClass = () => {
-        const today = new Date().toISOString().split('T')[0];
-        const tomorrow = new Date(Date.now() + 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
+        const today = getTodayDateString();
+        const tomorrow = getTomorrowDateString();
 
         if (dueDate === today) return 'border-blue-700 dark:text-white';
         if (dueDate === tomorrow) return 'border-blue-700 dark:text-white';
@@ -22,13 +20,9 @@ const TaskDueDate: React.FC<TaskDueDateProps> = ({ dueDate, className }) => {
     };
 
     const formatDueDate = () => {
-        const today = new Date().toISOString().split('T')[0];
-        const tomorrow = new Date(Date.now() + 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
-        const yesterday = new Date(Date.now() - 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
+        const today = getTodayDateString();
+        const tomorrow = getTomorrowDateString();
+        const yesterday = getYesterdayDateString();
 
         if (dueDate === today) return t('dateIndicators.today', 'TODAY');
         if (dueDate === tomorrow)
diff --git a/frontend/components/Task/TaskHeader.tsx b/frontend/components/Task/TaskHeader.tsx
index 32349c2..a63ca2f 100644
--- a/frontend/components/Task/TaskHeader.tsx
+++ b/frontend/components/Task/TaskHeader.tsx
@@ -16,7 +16,7 @@ import { Task } from '../../entities/Task';
 import { fetchSubtasks } from '../../utils/tasksService';
 import { isTaskCompleted, isTaskInProgress } from '../../constants/taskStatus';
 import TaskStatusControl from './TaskStatusControl';
-import { parseDateString } from '../../utils/dateUtils';
+import { parseDateString, getTodayDateString, getTomorrowDateString, getYesterdayDateString } from '../../utils/dateUtils';
 
 interface TaskHeaderProps {
     task: Task;
@@ -90,13 +90,9 @@ const TaskHeader: React.FC<TaskHeaderProps> = ({
     };
 
     const formatDueDate = (dueDate: string) => {
-        const today = new Date().toISOString().split('T')[0];
-        const tomorrow = new Date(Date.now() + 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
-        const yesterday = new Date(Date.now() - 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
+        const today = getTodayDateString();
+        const tomorrow = getTomorrowDateString();
+        const yesterday = getYesterdayDateString();
 
         if (dueDate === today) return t('dateIndicators.today', 'TODAY');
         if (dueDate === tomorrow)
diff --git a/frontend/components/Task/TaskTimeline.tsx b/frontend/components/Task/TaskTimeline.tsx
index dcf1f1b..25c8ef4 100644
--- a/frontend/components/Task/TaskTimeline.tsx
+++ b/frontend/components/Task/TaskTimeline.tsx
@@ -11,6 +11,7 @@ import {
     ExclamationTriangleIcon,
     SparklesIcon,
 } from '@heroicons/react/24/outline';
+import { getTodayDateString, getTomorrowDateString, getYesterdayDateString } from '../../utils/dateUtils';
 
 interface TaskTimelineProps {
     taskUid: string | undefined;
@@ -177,15 +178,11 @@ const TaskTimeline: React.FC<TaskTimelineProps> = ({ taskUid, refreshKey }) => {
         // Handle ISO date strings (e.g., "2025-07-15T00:00:00.000Z")
         const date = new Date(dateString);
 
-        // Check if it's today, tomorrow, or yesterday
-        const today = new Date().toISOString().split('T')[0];
-        const tomorrow = new Date(Date.now() + 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
-        const yesterday = new Date(Date.now() - 24 * 60 * 60 * 1000)
-            .toISOString()
-            .split('T')[0];
-        const dateOnly = date.toISOString().split('T')[0];
+        // Check if it's today, tomorrow, or yesterday using local time
+        const today = getTodayDateString();
+        const tomorrow = getTomorrowDateString();
+        const yesterday = getYesterdayDateString();
+        const dateOnly = dateString.split('T')[0];
 
         if (dateOnly === today) return t('dateIndicators.today');
         if (dateOnly === tomorrow) return t('dateIndicators.tomorrow');
diff --git a/frontend/utils/dateUtils.ts b/frontend/utils/dateUtils.ts
index 5ea32eb..d1722d5 100644
--- a/frontend/utils/dateUtils.ts
+++ b/frontend/utils/dateUtils.ts
@@ -25,6 +25,31 @@ export const getTodayDateString = (): string => {
     return `${year}-${month}-${day}`;
 };
 
+export const getTomorrowDateString = (): string => {
+    const d = new Date();
+    d.setDate(d.getDate() + 1);
+    const year = d.getFullYear();
+    const month = String(d.getMonth() + 1).padStart(2, '0');
+    const day = String(d.getDate()).padStart(2, '0');
+    return `${year}-${month}-${day}`;
+};
+
+export const getYesterdayDateString = (): string => {
+    const d = new Date();
+    d.setDate(d.getDate() - 1);
+    const year = d.getFullYear();
+    const month = String(d.getMonth() + 1).padStart(2, '0');
+    const day = String(d.getDate()).padStart(2, '0');
+    return `${year}-${month}-${day}`;
+};
+
+export const toLocalDateString = (date: Date): string => {
+    const year = date.getFullYear();
+    const month = String(date.getMonth() + 1).padStart(2, '0');
+    const day = String(date.getDate()).padStart(2, '0');
+    return `${year}-${month}-${day}`;
+};
+
 let userTimezone: string | null = null;
 
 export const setUserTimezone = (timezone: string): void => {