diff --git a/web/src/components/SessionList.directory-action.test.tsx b/web/src/components/SessionList.directory-action.test.tsx
index cc5be45f..962a909e 100644
--- a/web/src/components/SessionList.directory-action.test.tsx
+++ b/web/src/components/SessionList.directory-action.test.tsx
@@ -143,8 +143,13 @@ describe('SessionList time filter', () => {
         expect(screen.getByRole('button', { name: /Old session/ })).toBeInTheDocument()
 
         fireEvent.click(screen.getByRole('button', { name: 'Filter sessions by last activity' }))
-        fireEvent.click(screen.getByRole('button', { name: new Date(2026, 6, 17).toLocaleDateString() }))
-        fireEvent.click(screen.getByRole('button', { name: new Date(2026, 6, 18).toLocaleDateString() }))
+        const emptyDate = screen.getByRole('button', { name: new Date(2026, 6, 17).toLocaleDateString() })
+        const activeDate = screen.getByRole('button', { name: `${new Date(2026, 6, 18).toLocaleDateString()}, has session activity` })
+        expect(emptyDate).toHaveClass('text-[var(--app-hint)]')
+        expect(activeDate).toHaveClass('text-[var(--app-fg)]')
+        expect(activeDate).toHaveAttribute('title', `${new Date(2026, 6, 18).toLocaleDateString()}, has session activity`)
+        fireEvent.click(emptyDate)
+        fireEvent.click(activeDate)
 
         expect(screen.getByRole('button', { name: /Recent session/ })).toBeInTheDocument()
         expect(screen.queryByRole('button', { name: /Old session/ })).toBeNull()
@@ -174,7 +179,7 @@ describe('SessionList time filter', () => {
         fireEvent.click(filterButton)
         fireEvent.click(screen.getByRole('button', { name: new Date(2026, 6, 1).toLocaleDateString() }))
         expect(screen.getByText('Select end date')).toBeInTheDocument()
-        fireEvent.click(screen.getByRole('button', { name: new Date(2026, 6, 18).toLocaleDateString() }))
+        fireEvent.click(screen.getByRole('button', { name: `${new Date(2026, 6, 18).toLocaleDateString()}, has session activity` }))
 
         expect(filterButton).toHaveAttribute('aria-expanded', 'false')
         expect(filterButton).toHaveAttribute('title', '2026-07-01 – 2026-07-18')
diff --git a/web/src/components/SessionList.tsx b/web/src/components/SessionList.tsx
index 66f233d7..6be8da1b 100644
--- a/web/src/components/SessionList.tsx
+++ b/web/src/components/SessionList.tsx
@@ -573,6 +573,7 @@ function formatDateValue(date: Date): string {
 function SessionDateRangePicker(props: {
     start: string
     end: string
+    sessionActivityDates: ReadonlySet<string>
     onChange: (start: string, end: string) => void
     onClose: () => void
 }) {
@@ -627,17 +628,24 @@ function SessionDateRangePicker(props: {
                     const value = formatDateValue(date)
                     const isEndpoint = value === props.start || value === props.end
                     const isInRange = Boolean(props.start && props.end && value > props.start && value < props.end)
+                    const hasSessionActivity = props.sessionActivityDates.has(value)
+                    const dateLabel = date.toLocaleDateString()
+                    const activityLabel = hasSessionActivity
+                        ? t('sessions.timeFilter.dayWithActivity', { date: dateLabel })
+                        : dateLabel
                     return (
                         <button
                             key={value}
                             type="button"
                             onClick={() => selectDate(value)}
-                            aria-label={date.toLocaleDateString()}
+                            aria-label={activityLabel}
+                            title={hasSessionActivity ? activityLabel : undefined}
                             className={cn(
                                 'h-8 rounded-lg text-xs transition-colors',
                                 isEndpoint && 'bg-[var(--app-link)] text-white',
                                 isInRange && 'bg-[var(--app-link)]/15 text-[var(--app-link)]',
-                                !isEndpoint && !isInRange && 'hover:bg-[var(--app-subtle-bg)]'
+                                !isEndpoint && !isInRange && hasSessionActivity && 'text-[var(--app-fg)] hover:bg-[var(--app-subtle-bg)]',
+                                !isEndpoint && !isInRange && !hasSessionActivity && 'text-[var(--app-hint)] hover:bg-[var(--app-subtle-bg)]'
                             )}
                         >
                             {index + 1}
@@ -668,6 +676,7 @@ function SessionListSearch(props: {
     onChange: (value: string) => void
     customStart: string
     customEnd: string
+    sessionActivityDates: ReadonlySet<string>
     onDateRangeChange: (start: string, end: string) => void
 }) {
     const { t } = useTranslation()
@@ -719,6 +728,7 @@ function SessionListSearch(props: {
                             <SessionDateRangePicker
                                 start={props.customStart}
                                 end={props.customEnd}
+                                sessionActivityDates={props.sessionActivityDates}
                                 onChange={props.onDateRangeChange}
                                 onClose={() => setDatePickerOpen(false)}
                             />
@@ -1051,6 +1061,10 @@ export function SessionList(props: {
         },
         [props.sessions, selectedSessionId, showActiveSessionsOnly]
     )
+    const sessionActivityDates = useMemo(
+        () => new Set(allSessions.map(session => formatDateValue(new Date(session.updatedAt)))),
+        [allSessions]
+    )
     const visibleSessions = useMemo(
         () => isFiltering
             ? allSessions.filter(session => (
@@ -1246,6 +1260,7 @@ export function SessionList(props: {
                     onChange={setSearchQuery}
                     customStart={customStart}
                     customEnd={customEnd}
+                    sessionActivityDates={sessionActivityDates}
                     onDateRangeChange={(start, end) => {
                         setCustomStart(start)
                         setCustomEnd(end)
diff --git a/web/src/lib/locales/en.ts b/web/src/lib/locales/en.ts
index 37602758..cfa3c02f 100644
--- a/web/src/lib/locales/en.ts
+++ b/web/src/lib/locales/en.ts
@@ -60,6 +60,7 @@ export default {
   'sessions.timeFilter.close': 'Close date picker',
   'sessions.timeFilter.previousMonth': 'Previous month',
   'sessions.timeFilter.nextMonth': 'Next month',
+  'sessions.timeFilter.dayWithActivity': '{date}, has session activity',
   'sessions.group.showMore': 'Show {n} more',
   'sessions.group.showLess': 'Show less',
   'sessions.group.new': 'New session in this directory',
diff --git a/web/src/lib/locales/zh-CN.ts b/web/src/lib/locales/zh-CN.ts
index 67577348..039be865 100644
--- a/web/src/lib/locales/zh-CN.ts
+++ b/web/src/lib/locales/zh-CN.ts
@@ -60,6 +60,7 @@ export default {
   'sessions.timeFilter.close': '关闭日期选择器',
   'sessions.timeFilter.previousMonth': '上个月',
   'sessions.timeFilter.nextMonth': '下个月',
+  'sessions.timeFilter.dayWithActivity': '{date}，有会话活动',
   'sessions.group.showMore': '再显示 {n} 个',
   'sessions.group.showLess': '收起',
   'sessions.group.new': '在此目录新建会话',