diff --git a/src/package/rangeflow/components/DateSlider/DateLabelsTrack.tsx b/src/package/rangeflow/components/DateSlider/DateLabelsTrack.tsx
index 0a2b18a..c5dda46 100644
--- a/src/package/rangeflow/components/DateSlider/DateLabelsTrack.tsx
+++ b/src/package/rangeflow/components/DateSlider/DateLabelsTrack.tsx
@@ -1,11 +1,11 @@
 import clsx from 'clsx'
-import dayjs from 'dayjs'
 import { createElement, memo, useMemo } from 'react'
 
 import { OdometerText } from '../../animations/OdometerText'
 import { useDaysInRange } from '../../hooks/use-days-in-range'
 import { useRangeFlowSlots } from '../../hooks/use-rangeflow-slots'
 import { useRangeFlowStore } from '../../hooks/use-rangeflow-store'
+import { normalizeDateRange } from '../../utils/normalize-date-range'
 
 function getLabelFormat(daysInRange: number): string {
   if (daysInRange > 120) {
@@ -42,12 +42,13 @@ export const DateLabelsTrack = memo(() => {
 
   const labels = useMemo(() => {
     const format = getLabelFormat(daysInRange)
-    const count = getLabelCount(daysInRange)
-    const start = dayjs(range.from)
-    const totalMs = dayjs(range.to).diff(start)
+    const count = Math.max(getLabelCount(daysInRange), 1)
+    const { start, end } = normalizeDateRange(range)
+    const totalMs = end.diff(start)
+    const steps = Math.max(count - 1, 1)
 
     return Array.from({ length: count }, (_, i) => {
-      const ratio = i / (count - 1)
+      const ratio = i / steps
 
       return start.add(totalMs * ratio, 'ms').format(format)
     })
diff --git a/src/package/rangeflow/components/DateSlider/SliderValue.tsx b/src/package/rangeflow/components/DateSlider/SliderValue.tsx
index 9a268f4..d4fceca 100644
--- a/src/package/rangeflow/components/DateSlider/SliderValue.tsx
+++ b/src/package/rangeflow/components/DateSlider/SliderValue.tsx
@@ -11,7 +11,13 @@ export const SliderValue = memo(() => {
   const selected = useRangeFlowStore(state => state.selected_date)
 
   const label = useMemo(() => {
-    const days = dayjs(selected.to).diff(selected.from, 'day') + 1
+    const from = dayjs(selected.from)
+    const to = dayjs(selected.to)
+
+    const safeFrom = from.isValid() ? from : to
+    const safeTo = to.isValid() ? to : from
+    const rawDays = safeTo.isValid() && safeFrom.isValid() ? safeTo.diff(safeFrom, 'day') + 1 : 1
+    const days = Number.isFinite(rawDays) ? Math.max(rawDays, 1) : 1
 
     if (size < 10) {
       return `${days}D`
diff --git a/src/package/rangeflow/components/PickerBar/CalendarPopover.tsx b/src/package/rangeflow/components/PickerBar/CalendarPopover.tsx
index 755e623..2e2ef96 100644
--- a/src/package/rangeflow/components/PickerBar/CalendarPopover.tsx
+++ b/src/package/rangeflow/components/PickerBar/CalendarPopover.tsx
@@ -25,15 +25,28 @@ export function CalendarPopover({ children }: Props) {
   } = useRangeFlowRefs()
 
   const extendRange = () => {
-    let rangeFrom = dayjs(range.from)
-    let rangeTo = dayjs(range.to)
+    const rangeFromDate = dayjs(range.from)
+    const rangeToDate = dayjs(range.to)
+    const selectedFrom = dayjs(date.from)
+    const selectedTo = dayjs(date.to)
 
-    if (dayjs(date.from).isBefore(rangeFrom)) {
-      rangeFrom = dayjs(date.from).subtract(10, 'day')
+    let rangeFrom = rangeFromDate.isValid() ? rangeFromDate : dayjs()
+    let rangeTo = rangeToDate.isValid() ? rangeToDate : rangeFrom
+
+    if (rangeTo.isBefore(rangeFrom)) {
+      rangeTo = rangeFrom
+    }
+
+    if (selectedFrom.isValid() && selectedFrom.isBefore(rangeFrom)) {
+      rangeFrom = selectedFrom.subtract(10, 'day')
     }
 
-    if (dayjs(date.to).isAfter(rangeTo)) {
-      rangeTo = dayjs(date.to).add(10, 'day')
+    if (selectedTo.isValid() && selectedTo.isAfter(rangeTo)) {
+      rangeTo = selectedTo.add(10, 'day')
+    }
+
+    if (rangeTo.isBefore(rangeFrom)) {
+      rangeTo = rangeFrom.add(1, 'day')
     }
 
     return {
@@ -67,7 +80,7 @@ export function CalendarPopover({ children }: Props) {
       <PopoverTrigger className="cursor-pointer">{children}</PopoverTrigger>
       <PopoverContent align="start" sideOffset={10}>
         <Calendar
-          defaultMonth={date.from}
+          defaultMonth={dayjs(date.from).isValid() ? date.from : undefined}
           numberOfMonths={2}
           showOutsideDays={false}
           {...CalendarProps}
@@ -81,13 +94,18 @@ export function CalendarPopover({ children }: Props) {
               return
             }
 
-            const nextSelected = {
-              from: dayjs(nextDate.from).startOf('day').toDate(),
-              to: dayjs(nextDate.to).startOf('day').toDate()
+            const from = dayjs(nextDate.from).startOf('day')
+            const to = dayjs(nextDate.to).startOf('day')
+
+            if (!from.isValid() || !to.isValid()) {
+              return
             }
 
             update({
-              selected_date: nextSelected
+              selected_date: {
+                from: from.toDate(),
+                to: to.toDate()
+              }
             })
           }}
         />
diff --git a/src/package/rangeflow/components/PickerBar/SelectedDate.tsx b/src/package/rangeflow/components/PickerBar/SelectedDate.tsx
index 311adc9..ca1090d 100644
--- a/src/package/rangeflow/components/PickerBar/SelectedDate.tsx
+++ b/src/package/rangeflow/components/PickerBar/SelectedDate.tsx
@@ -14,19 +14,18 @@ export function SelectedDate() {
 
     const start = dayjs(date.from)
     const end = dayjs(date.to)
-
     const formatter = start.isSame(end, 'year') ? 'DD MMM' : 'DD MMM YYYY'
 
     const labels = {
-      from: start.format(formatter),
-      to: end.format(formatter)
+      from: start.isValid() ? start.format(formatter) : 'Invalid Date',
+      to: end.isValid() ? end.format(formatter) : 'Invalid Date'
     }
 
-    if (today.isSame(start, 'day')) {
+    if (start.isValid() && today.isSame(start, 'day')) {
       labels.from = 'Today'
     }
 
-    if (today.isSame(end, 'day')) {
+    if (end.isValid() && today.isSame(end, 'day')) {
       labels.to = 'Today'
     }
 
diff --git a/src/package/rangeflow/hooks/use-days-in-range.ts b/src/package/rangeflow/hooks/use-days-in-range.ts
index 79b1e91..4b892b0 100644
--- a/src/package/rangeflow/hooks/use-days-in-range.ts
+++ b/src/package/rangeflow/hooks/use-days-in-range.ts
@@ -1,8 +1,12 @@
-import dayjs from 'dayjs'
 import { useMemo } from 'react'
 
 import type { DateRange } from '../types'
+import { normalizeDateRange } from '../utils/normalize-date-range'
 
 export function useDaysInRange(range: DateRange) {
-  return useMemo(() => dayjs(range.to).diff(dayjs(range.from), 'day'), [range.from, range.to])
+  return useMemo(() => {
+    const { start, end } = normalizeDateRange(range)
+    const rawDiff = end.diff(start, 'day')
+    return Number.isFinite(rawDiff) ? Math.max(rawDiff + 1, 1) : 1
+  }, [range.from, range.to])
 }
diff --git a/src/package/rangeflow/utils/create-slider-values.ts b/src/package/rangeflow/utils/create-slider-values.ts
index 15766d6..bc6a1b1 100644
--- a/src/package/rangeflow/utils/create-slider-values.ts
+++ b/src/package/rangeflow/utils/create-slider-values.ts
@@ -4,6 +4,7 @@ import { SLIDER_THUMB_MIN_SIZE } from '../constants/slider'
 import type { DateRange } from '../types'
 import { clamp } from './clamp'
 import { interpolate } from './interpolate'
+import { normalizeDateRange } from './normalize-date-range'
 
 const toVisual = interpolate([1, 100], [SLIDER_THUMB_MIN_SIZE, 100])
 
@@ -14,14 +15,31 @@ export function createSliderValues(
     to: Date
   }
 ) {
-  const rangeStart = dayjs(range.from).startOf('day')
-  const daysInRange = dayjs(range.to).startOf('day').diff(rangeStart, 'day')
+  const { start: rangeStart, end: rangeEnd } = normalizeDateRange(range)
 
-  const fromDay = dayjs(selected.from).startOf('day')
-  const toDay = dayjs(selected.to).startOf('day')
+  const rawRangeDays = rangeEnd.diff(rangeStart, 'day')
+  const daysInRange = Number.isFinite(rawRangeDays)
+    ? Math.max(rawRangeDays + 1, 1)
+    : 1
 
-  const pastDays = Math.max(fromDay.diff(rangeStart, 'day'), 0)
-  const selectedDays = toDay.diff(fromDay, 'day') + 1
+  const fromDay = dayjs(selected.from)
+  const toDay = dayjs(selected.to)
+  const safeFrom = fromDay.isValid() ? fromDay.startOf('day') : rangeStart
+  let safeTo = toDay.isValid() ? toDay.startOf('day') : safeFrom
+
+  if (safeTo.isBefore(safeFrom)) {
+    safeTo = safeFrom
+  }
+
+  const rawPastDays = safeFrom.diff(rangeStart, 'day')
+  const pastDays = Number.isFinite(rawPastDays)
+    ? Math.max(Math.min(rawPastDays, daysInRange - 1), 0)
+    : 0
+
+  const rawSelectedDays = safeTo.diff(safeFrom, 'day') + 1
+  const selectedDays = Number.isFinite(rawSelectedDays)
+    ? Math.max(Math.min(rawSelectedDays, daysInRange), 1)
+    : 1
 
   const rawSize = (selectedDays * 100) / daysInRange
   const rawLeft = (pastDays * 100) / daysInRange
diff --git a/src/package/rangeflow/utils/derive-selection-from-layout.ts b/src/package/rangeflow/utils/derive-selection-from-layout.ts
index f14ea8b..9c7dbf1 100644
--- a/src/package/rangeflow/utils/derive-selection-from-layout.ts
+++ b/src/package/rangeflow/utils/derive-selection-from-layout.ts
@@ -10,6 +10,7 @@ import {
 import type { DateRange } from '../types'
 import { clamp } from './clamp'
 import { interpolate } from './interpolate'
+import { normalizeDateRange } from './normalize-date-range'
 
 // Inverse of the `toVisual` mapping in createSliderValues: [MIN, 100] → [1, 100].
 const fromVisual = interpolate([SLIDER_THUMB_MIN_SIZE, 100], [1, 100])
@@ -21,20 +22,29 @@ export function deriveSelectionFromLayout(layout: Layout, range: DateRange) {
   const left = layout[SLIDER_LEFT_SPACER]
   const right = layout[SLIDER_RIGHT_SPACER]
 
-  const start = dayjs(range.from).startOf('day')
-  const daysInRange = dayjs(range.to).startOf('day').diff(start, 'day')
+  const { start, end } = normalizeDateRange(range)
+  const rawRangeDays = end.diff(start, 'day')
+  const daysInRange = Number.isFinite(rawRangeDays)
+    ? Math.max(rawRangeDays + 1, 1)
+    : 1
+
+  const safeSize = Number.isFinite(size) ? size : SLIDER_THUMB_MIN_SIZE
+  const safeLeft = Number.isFinite(left) ? left : 0
+  const safeRight = Number.isFinite(right)
+    ? right
+    : Math.max(100 - safeLeft - safeSize, 0)
+  const actualSize = fromVisual(safeSize)
+  const actualLeft = safeLeft + (safeSize - actualSize)
 
   // Undo the inflation createSliderValues applied to size (absorbed by the
   // left spacer). The right spacer is already unscaled, so no inversion there.
-  const actualSize = fromVisual(size)
-  const actualLeft = left + (size - actualSize)
 
   // Derive totalDays from the thumb width (the authoritative value), not from
   // the leftover between startDay and trailingDays — otherwise independent
   // rounding of the two spacers can flip the selection length by ±1 day
   // while the user is only translating the thumb across the track.
   const totalDays =
-    Math.round(size) <= SLIDER_THUMB_MIN_SIZE
+    Math.round(safeSize) <= SLIDER_THUMB_MIN_SIZE
       ? 1
       : Math.max(Math.round((actualSize * daysInRange) / 100), 1)
 
diff --git a/src/package/rangeflow/utils/normalize-date-range.ts b/src/package/rangeflow/utils/normalize-date-range.ts
new file mode 100644
index 0000000..f837f89
--- /dev/null
+++ b/src/package/rangeflow/utils/normalize-date-range.ts
@@ -0,0 +1,17 @@
+import dayjs from 'dayjs'
+import type { DateRange } from '../types'
+
+export function normalizeDateRange(range: DateRange) {
+  const now = dayjs().startOf('day')
+  const startDate = dayjs(range.from)
+  const endDate = dayjs(range.to)
+
+  const start = startDate.isValid() ? startDate.startOf('day') : now
+  let end = endDate.isValid() ? endDate.startOf('day') : start
+
+  if (end.isBefore(start)) {
+    end = start
+  }
+
+  return { start, end }
+}