diff --git a/apps/api/src/app/portfolio/calculator/portfolio-calculator.ts b/apps/api/src/app/portfolio/calculator/portfolio-calculator.ts
index 1527c4bd3b..ca440c6d2a 100644
--- a/apps/api/src/app/portfolio/calculator/portfolio-calculator.ts
+++ b/apps/api/src/app/portfolio/calculator/portfolio-calculator.ts
@@ -1418,14 +1418,8 @@ export abstract class PortfolioCalculator {
     let netPerformanceAtStartDate: number;
     let netPerformanceWithCurrencyEffectAtStartDate: number;
 
-    // The historical data items are dated at midnight in UTC, hence a start
-    // or an end at the end of a day in the time zone of the instance is
-    // changed to this date
-    const endDate = isEqual(end, endOfDay(end)) ? resetHours(end) : end;
-
-    const startDate = isEqual(start, endOfDay(start))
-      ? resetHours(start)
-      : start;
+    const endDate = this.toChartDate(end);
+    const startDate = this.toChartDate(start);
 
     for (const historicalDataItem of historicalData) {
       const date = resetHours(parseDate(historicalDataItem.date));
@@ -1920,4 +1914,8 @@ export abstract class PortfolioCalculator {
       await this.initialize(attempt + 1);
     }
   }
+
+  private toChartDate(aDate: Date) {
+    return isEqual(aDate, endOfDay(aDate)) ? resetHours(aDate) : aDate;
+  }
 }
diff --git a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.spec.ts b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.spec.ts
index 9589132372..43ff160a78 100644
--- a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.spec.ts
+++ b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.spec.ts
@@ -1,3 +1,7 @@
+/**
+ * @jest-environment <rootDir>/jest-environment-tz.js
+ * @jest-environment-options {"timeZone": "America/New_York"}
+ */
 import { PortfolioCalculator } from '@ghostfolio/api/app/portfolio/calculator/portfolio-calculator';
 import { userDummyData } from '@ghostfolio/api/app/portfolio/calculator/portfolio-calculator-test-utils';
 import { PortfolioCalculatorFactory } from '@ghostfolio/api/app/portfolio/calculator/portfolio-calculator.factory';
@@ -186,10 +190,6 @@ describe('PortfolioCalculator', () => {
   });
 
   describe('get performance', () => {
-    // The chart items are dated at midnight in UTC, but a calendar year date
-    // range ends at the end of 31 December in the time zone of the instance.
-    // Hence this test must give the same result with the instance in any time
-    // zone. Set TEST_TZ to run it with the instance in another time zone.
     it('with a calendar year date range', async () => {
       const snapshot = await portfolioCalculator.getSnapshot();