diff --git a/components.d.ts b/components.d.ts
index c1719787..5da66697 100644
--- a/components.d.ts
+++ b/components.d.ts
@@ -67,6 +67,7 @@ declare module '@vue/runtime-core' {
     CTooltip: typeof import('./src/ui/c-tooltip/c-tooltip.vue')['default']
     'CTooltip.demo': typeof import('./src/ui/c-tooltip/c-tooltip.demo.vue')['default']
     CurlToCode: typeof import('./src/tools/curl-to-code/curl-to-code.vue')['default']
+    DateCalculator: typeof import('./src/tools/date-calculator/date-calculator.vue')['default']
     DateTimeConverter: typeof import('./src/tools/date-time-converter/date-time-converter.vue')['default']
     'DemoHome.page': typeof import('./src/ui/demo/demo-home.page.vue')['default']
     DemoWrapper: typeof import('./src/ui/demo/demo-wrapper.vue')['default']
diff --git a/locales/en.yml b/locales/en.yml
index cab2c618..befdf937 100644
--- a/locales/en.yml
+++ b/locales/en.yml
@@ -297,6 +297,25 @@ tools:
     title: JWT parser
     description: Parse and decode your JSON Web Token (jwt) and display its content.
 
+  date-calculator:
+    title: Date calculator
+    description: Add or subtract days from a date, or calculate the number of days between two dates.
+    offset:
+      sectionTitle: Date after / before N days
+      baseDate: Start date
+      days: Days offset
+      daysHint: Use a negative number to go backwards
+      resultLabel: Result date
+    diff:
+      sectionTitle: Days between two dates
+      startDate: Start date
+      targetDate: Target date
+      resultLabel: Difference
+      dayUnit: days
+      directionAfter: Target date is after the start date
+      directionBefore: Target date is before the start date
+      directionSame: Same date
+
   date-converter:
     title: Date-time converter
     description: Convert date and time into the various different formats
diff --git a/locales/zh.yml b/locales/zh.yml
index 9135b32b..65d24c17 100644
--- a/locales/zh.yml
+++ b/locales/zh.yml
@@ -293,6 +293,25 @@ tools:
     title: JWT 解析器
     description: 解析和解码JSON Web Token（jwt）并显示其内容。
 
+  date-calculator:
+    title: 日期计算器
+    description: 推算几天前/后的日期，或计算两个日期之间相差的天数。
+    offset:
+      sectionTitle: 推算几天前 / 后的日期
+      baseDate: 起始日期
+      days: 偏移天数
+      daysHint: 输入负数则往前推算
+      resultLabel: 结果日期
+    diff:
+      sectionTitle: 计算两个日期相差
+      startDate: 开始日期
+      targetDate: 目标日期
+      resultLabel: 相差
+      dayUnit: 天
+      directionAfter: 目标日期比起始日期晚
+      directionBefore: 目标日期比起始日期早
+      directionSame: 两个日期为同一天
+
   date-converter:
     title: 日期时间转换器
     description: 将日期和时间转换为各种不同的格式
diff --git a/src/tools/date-calculator/date-calculator.vue b/src/tools/date-calculator/date-calculator.vue
new file mode 100644
index 00000000..621b2c4d
--- /dev/null
+++ b/src/tools/date-calculator/date-calculator.vue
@@ -0,0 +1,141 @@
+<script setup lang="ts">
+import { addDays, differenceInCalendarDays, format, isValid } from 'date-fns';
+import { enUS, zhCN } from 'date-fns/locale';
+import { useI18n } from 'vue-i18n';
+
+const { t, locale } = useI18n();
+
+const DAY_MS = 24 * 60 * 60 * 1000;
+
+// 今天 0 点的时间戳（去掉时分秒，避免日期计算受时分影响）
+function startOfToday() {
+  const now = new Date();
+  return new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime();
+}
+
+// 功能一：推算几天前 / 后的日期
+const offsetBaseDate = ref<number>(startOfToday());
+const offsetDays = ref(30);
+
+// 功能二：计算两个日期相差的天数
+const diffStartDate = ref<number>(startOfToday());
+const diffTargetDate = ref<number>(startOfToday() + 30 * DAY_MS);
+
+// 按当前语言选择 date-fns 的 locale 与日期格式
+const dateLocale = computed(() => (locale.value?.startsWith('zh') ? zhCN : enUS));
+const datePattern = computed(() =>
+  locale.value?.startsWith('zh') ? 'yyyy年M月d日 EEEE' : 'EEEE, MMMM d, yyyy',
+);
+
+const offsetResultDate = computed(() => {
+  if (offsetBaseDate.value == null || !Number.isFinite(offsetDays.value)) {
+    return null;
+  }
+  const base = new Date(offsetBaseDate.value);
+  return isValid(base) ? addDays(base, offsetDays.value) : null;
+});
+
+const offsetResultText = computed(() => {
+  const date = offsetResultDate.value;
+  if (!date || !isValid(date)) {
+    return '';
+  }
+  return format(date, datePattern.value, { locale: dateLocale.value });
+});
+
+const diffDays = computed(() => {
+  if (diffStartDate.value == null || diffTargetDate.value == null) {
+    return null;
+  }
+  const start = new Date(diffStartDate.value);
+  const target = new Date(diffTargetDate.value);
+  if (!isValid(start) || !isValid(target)) {
+    return null;
+  }
+  return differenceInCalendarDays(target, start);
+});
+
+const absDiffDays = computed(() => (diffDays.value === null ? null : Math.abs(diffDays.value)));
+</script>
+
+<template>
+  <div style="flex: 0 0 100%">
+    <div style="margin: 0 auto; max-width: 620px">
+      <!-- 功能一：推算几天前 / 后的日期 -->
+      <c-card mb-4 :title="t('tools.date-calculator.offset.sectionTitle')">
+        <n-form-item :label="t('tools.date-calculator.offset.baseDate')" :show-feedback="false">
+          <n-date-picker v-model:value="offsetBaseDate" type="date" />
+        </n-form-item>
+
+        <n-form-item
+          mt-4
+          :label="t('tools.date-calculator.offset.days')"
+          :show-feedback="false"
+        >
+          <div w-full flex items-center gap-3>
+            <n-input-number v-model:value="offsetDays" />
+            <span whitespace-nowrap text-sm op-60>
+              {{ t('tools.date-calculator.offset.daysHint') }}
+            </span>
+          </div>
+        </n-form-item>
+
+        <n-divider />
+
+        <div flex justify-center>
+          <n-statistic :label="t('tools.date-calculator.offset.resultLabel')">
+            {{ offsetResultText || '—' }}
+          </n-statistic>
+        </div>
+      </c-card>
+
+      <!-- 功能二：计算两个日期相差的天数 -->
+      <c-card :title="t('tools.date-calculator.diff.sectionTitle')">
+        <n-form-item :label="t('tools.date-calculator.diff.startDate')" :show-feedback="false">
+          <n-date-picker v-model:value="diffStartDate" type="date" />
+        </n-form-item>
+
+        <n-form-item
+          mt-4
+          :label="t('tools.date-calculator.diff.targetDate')"
+          :show-feedback="false"
+        >
+          <n-date-picker v-model:value="diffTargetDate" type="date" />
+        </n-form-item>
+
+        <n-divider />
+
+        <div flex flex-col items-center gap-2>
+          <n-statistic :label="t('tools.date-calculator.diff.resultLabel')">
+            <span>{{ absDiffDays === null ? '—' : absDiffDays }}</span>
+            <span text-sm font-normal op-70>
+              {{ t('tools.date-calculator.diff.dayUnit') }}
+            </span>
+          </n-statistic>
+          <div text-sm op-60>
+            <span v-if="diffDays === null || diffDays === 0">
+              {{ t('tools.date-calculator.diff.directionSame') }}
+            </span>
+            <span v-else-if="diffDays > 0">
+              {{ t('tools.date-calculator.diff.directionAfter') }}
+            </span>
+            <span v-else>
+              {{ t('tools.date-calculator.diff.directionBefore') }}
+            </span>
+          </div>
+        </div>
+      </c-card>
+    </div>
+  </div>
+</template>
+
+<style lang="less" scoped>
+.n-date-picker,
+.n-input-number {
+  width: 100%;
+}
+
+.n-input-number {
+  max-width: 220px;
+}
+</style>
diff --git a/src/tools/date-calculator/index.ts b/src/tools/date-calculator/index.ts
new file mode 100644
index 00000000..2ab05e53
--- /dev/null
+++ b/src/tools/date-calculator/index.ts
@@ -0,0 +1,13 @@
+import { Calculator } from '@vicons/tabler';
+import { defineTool } from '../tool';
+import { translate } from '@/plugins/i18n.plugin';
+
+export const tool = defineTool({
+  name: translate('tools.date-calculator.title'),
+  path: '/date-calculator',
+  description: translate('tools.date-calculator.description'),
+  keywords: ['date', 'difference', 'days', 'calculator', 'add', 'subtract', 'duration', 'between', 'offset'],
+  component: () => import('./date-calculator.vue'),
+  icon: Calculator,
+  createdAt: new Date('2026-06-15'),
+});
diff --git a/src/tools/index.ts b/src/tools/index.ts
index 4bc036c1..3414b675 100644
--- a/src/tools/index.ts
+++ b/src/tools/index.ts
@@ -61,6 +61,7 @@ import { tool as chmodCalculator } from './chmod-calculator';
 import { tool as chronometer } from './chronometer';
 import { tool as colorConverter } from './color-converter';
 import { tool as crontabGenerator } from './crontab-generator';
+import { tool as dateCalculator } from './date-calculator';
 import { tool as dateTimeConverter } from './date-time-converter';
 import { tool as deviceInformation } from './device-information';
 import { tool as cypher } from './encryption';
@@ -127,6 +128,7 @@ export const toolsByCategory: ToolCategory[] = [
     name: 'Converter',
     components: [
       byteUnitConverter,
+      dateCalculator,
       dateTimeConverter,
       baseConverter,
       romanNumeralConverter,