diff --git a/web/components/charts/contract/binary.tsx b/web/components/charts/contract/binary.tsx
index 3526933f..a6ba9bee 100644
--- a/web/components/charts/contract/binary.tsx
+++ b/web/components/charts/contract/binary.tsx
@@ -49,24 +49,24 @@ export const BinaryContractChart = (props: {
   onMouseOver?: (p: HistoryPoint<Bet> | undefined) => void
 }) => {
   const { contract, bets, onMouseOver } = props
-  const [startDate, endDate] = getDateRange(contract)
+  const [start, end] = getDateRange(contract)
   const startP = getInitialProbability(contract)
   const endP = getProbability(contract)
   const betPoints = useMemo(() => getBetPoints(bets), [bets])
   const data = useMemo(() => {
     return [
-      { x: new Date(startDate), y: startP },
+      { x: new Date(start), y: startP },
       ...betPoints,
-      { x: new Date(endDate ?? Date.now() + DAY_MS), y: endP },
+      { x: new Date(end ?? Date.now() + DAY_MS), y: endP },
     ]
-  }, [startDate, startP, endDate, endP, betPoints])
+  }, [start, startP, end, endP, betPoints])
 
   const rightmostDate = getRightmostVisibleDate(
-    endDate ? new Date(endDate) : null,
-    last(betPoints)?.x,
-    new Date(Date.now())
+    end,
+    last(betPoints)?.x?.getTime(),
+    Date.now()
   )
-  const visibleRange = [startDate, rightmostDate]
+  const visibleRange = [start, rightmostDate]
   const isMobile = useIsMobile(800)
   const containerRef = useRef<HTMLDivElement>(null)
   const width = useElementWidth(containerRef) ?? 0
diff --git a/web/components/charts/contract/choice.tsx b/web/components/charts/contract/choice.tsx
index 52bae0f8..127e7d9c 100644
--- a/web/components/charts/contract/choice.tsx
+++ b/web/components/charts/contract/choice.tsx
@@ -146,9 +146,9 @@ export const ChoiceContractChart = (props: {
     [answers, contract, betPoints, start, end]
   )
   const rightmostDate = getRightmostVisibleDate(
-    end ? new Date(end) : null,
-    last(betPoints)?.x,
-    new Date(Date.now())
+    end,
+    last(betPoints)?.x?.getTime(),
+    Date.now()
   )
   const visibleRange = [start, rightmostDate]
   const isMobile = useIsMobile(800)
diff --git a/web/components/charts/contract/pseudo-numeric.tsx b/web/components/charts/contract/pseudo-numeric.tsx
index 4287a57e..1232a96c 100644
--- a/web/components/charts/contract/pseudo-numeric.tsx
+++ b/web/components/charts/contract/pseudo-numeric.tsx
@@ -62,7 +62,7 @@ export const PseudoNumericContractChart = (props: {
 }) => {
   const { contract, bets, onMouseOver } = props
   const { min, max, isLogScale } = contract
-  const [startDate, endDate] = getDateRange(contract)
+  const [start, end] = getDateRange(contract)
   const scaleP = useMemo(
     () => getScaleP(min, max, isLogScale),
     [min, max, isLogScale]
@@ -72,18 +72,18 @@ export const PseudoNumericContractChart = (props: {
   const betPoints = useMemo(() => getBetPoints(bets, scaleP), [bets, scaleP])
   const data = useMemo(
     () => [
-      { x: new Date(startDate), y: startP },
+      { x: new Date(start), y: startP },
       ...betPoints,
-      { x: new Date(endDate ?? Date.now() + DAY_MS), y: endP },
+      { x: new Date(end ?? Date.now() + DAY_MS), y: endP },
     ],
-    [betPoints, startDate, startP, endDate, endP]
+    [betPoints, start, startP, end, endP]
   )
   const rightmostDate = getRightmostVisibleDate(
-    endDate ? new Date(endDate) : null,
-    last(betPoints)?.x,
-    new Date(Date.now())
+    end,
+    last(betPoints)?.x?.getTime(),
+    Date.now()
   )
-  const visibleRange = [startDate, rightmostDate]
+  const visibleRange = [start, rightmostDate]
   const isMobile = useIsMobile(800)
   const containerRef = useRef<HTMLDivElement>(null)
   const width = useElementWidth(containerRef) ?? 0
diff --git a/web/components/charts/helpers.tsx b/web/components/charts/helpers.tsx
index fdbec204..ea436213 100644
--- a/web/components/charts/helpers.tsx
+++ b/web/components/charts/helpers.tsx
@@ -263,15 +263,15 @@ export const getDateRange = (contract: Contract) => {
 }
 
 export const getRightmostVisibleDate = (
-  contractEnd: Date | null | undefined,
-  lastActivity: Date | null | undefined,
-  now: Date
+  contractEnd: number | null | undefined,
+  lastActivity: number | null | undefined,
+  now: number
 ) => {
   if (contractEnd != null) {
     return contractEnd
   } else if (lastActivity != null) {
     // client-DB clock divergence may cause last activity to be later than now
-    return new Date(Math.max(lastActivity.getTime(), now.getTime()))
+    return Math.max(lastActivity, now)
   } else {
     return now
   }