diff --git a/apps/client/src/common/utils/__tests__/eventsManager.test.js b/apps/client/src/common/utils/__tests__/eventsManager.test.js
index c4ac98239..5b24034e8 100644
--- a/apps/client/src/common/utils/__tests__/eventsManager.test.js
+++ b/apps/client/src/common/utils/__tests__/eventsManager.test.js
@@ -1,127 +1,232 @@
 import { formatEventList, getEventsWithDelay, trimEventlist } from '../eventsManager';
 
-test('getEventsWithDelay function', () => {
-  const testData = [
-    {
-      title: 'Welcome to Ontime',
-      timeStart: 28800000,
-      timeEnd: 30600000,
-      colour: '',
-      type: 'event',
-      id: '5946',
-    },
-    {
-      duration: 60000,
-      type: 'delay',
-      id: '24240',
-    },
-    {
-      title: 'Unless recalled by the OSC address',
-      timeStart: 34920000,
-      timeEnd: 35520000,
-      colour: '',
-      type: 'event',
-      id: '8ee5',
-    },
-    {
-      title: 'Use simpler times to create a timer',
-      timeStart: 120000,
-      timeEnd: 720000,
-      colour: '',
-      type: 'event',
-      id: '8222',
-    },
-    {
-      duration: 900000,
-      type: 'delay',
-      revision: 0,
-      id: 'a386',
-    },
-    {
-      title: 'Add delay blocks to affect all events',
-      timeStart: 37320000,
-      timeEnd: 38520000,
-      colour: '',
-      type: 'event',
-      id: '6dce',
-    },
-    {
-      title: 'Add and remove events with [+] and [-]',
-      timeStart: 38520000,
-      timeEnd: 45120000,
-      colour: '',
-      type: 'event',
-      id: '2651',
-    },
-    {
-      type: 'block',
-      id: 'e6a1',
-    },
-    {
-      title: 'And control whether they are public',
-      timeStart: 46800000,
-      timeEnd: 57600000,
-      colour: '',
-      type: 'event',
-      id: '1358',
-    },
-  ];
+describe('getEventsWithDelay function', () => {
+  test('with positive delays', () => {
+    const testData = [
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 28800000,
+        timeEnd: 30600000,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+      {
+        duration: 60000,
+        type: 'delay',
+        id: '24240',
+      },
+      {
+        title: 'Unless recalled by the OSC address',
+        timeStart: 34920000,
+        timeEnd: 35520000,
+        colour: '',
+        type: 'event',
+        id: '8ee5',
+      },
+      {
+        title: 'Use simpler times to create a timer',
+        timeStart: 120000,
+        timeEnd: 720000,
+        colour: '',
+        type: 'event',
+        id: '8222',
+      },
+      {
+        duration: 900000,
+        type: 'delay',
+        revision: 0,
+        id: 'a386',
+      },
+      {
+        title: 'Add delay blocks to affect all events',
+        timeStart: 37320000,
+        timeEnd: 38520000,
+        colour: '',
+        type: 'event',
+        id: '6dce',
+      },
+      {
+        title: 'Add and remove events with [+] and [-]',
+        timeStart: 38520000,
+        timeEnd: 45120000,
+        colour: '',
+        type: 'event',
+        id: '2651',
+      },
+      {
+        type: 'block',
+        id: 'e6a1',
+      },
+      {
+        title: 'And control whether they are public',
+        timeStart: 46800000,
+        timeEnd: 57600000,
+        colour: '',
+        type: 'event',
+        id: '1358',
+      },
+    ];
 
-  const expected = [
-    {
-      title: 'Welcome to Ontime',
-      timeStart: 28800000,
-      timeEnd: 30600000,
-      colour: '',
-      type: 'event',
-      id: '5946',
-    },
-    {
-      title: 'Unless recalled by the OSC address',
-      timeStart: 34920000 + 60000,
-      timeEnd: 35520000 + 60000,
-      colour: '',
-      type: 'event',
-      id: '8ee5',
-    },
-    {
-      title: 'Use simpler times to create a timer',
-      timeStart: 120000 + 60000,
-      timeEnd: 720000 + 60000,
-      colour: '',
-      type: 'event',
-      id: '8222',
-    },
-    {
-      title: 'Add delay blocks to affect all events',
-      timeStart: 37320000 + 60000 + 900000,
-      timeEnd: 38520000 + 60000 + 900000,
-      colour: '',
-      type: 'event',
-      id: '6dce',
-    },
-    {
-      title: 'Add and remove events with [+] and [-]',
-      timeStart: 38520000 + 60000 + 900000,
-      timeEnd: 45120000 + 60000 + 900000,
-      colour: '',
-      type: 'event',
-      id: '2651',
-    },
-    {
-      title: 'And control whether they are public',
-      timeStart: 46800000,
-      timeEnd: 57600000,
-      colour: '',
-      type: 'event',
-      id: '1358',
-    },
-  ];
+    const expected = [
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 28800000,
+        timeEnd: 30600000,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+      {
+        title: 'Unless recalled by the OSC address',
+        timeStart: 34920000 + 60000,
+        timeEnd: 35520000 + 60000,
+        colour: '',
+        type: 'event',
+        id: '8ee5',
+      },
+      {
+        title: 'Use simpler times to create a timer',
+        timeStart: 120000 + 60000,
+        timeEnd: 720000 + 60000,
+        colour: '',
+        type: 'event',
+        id: '8222',
+      },
+      {
+        title: 'Add delay blocks to affect all events',
+        timeStart: 37320000 + 60000 + 900000,
+        timeEnd: 38520000 + 60000 + 900000,
+        colour: '',
+        type: 'event',
+        id: '6dce',
+      },
+      {
+        title: 'Add and remove events with [+] and [-]',
+        timeStart: 38520000 + 60000 + 900000,
+        timeEnd: 45120000 + 60000 + 900000,
+        colour: '',
+        type: 'event',
+        id: '2651',
+      },
+      {
+        title: 'And control whether they are public',
+        timeStart: 46800000,
+        timeEnd: 57600000,
+        colour: '',
+        type: 'event',
+        id: '1358',
+      },
+    ];
 
-  expect(getEventsWithDelay(testData)).toStrictEqual(expected);
+    expect(getEventsWithDelay(testData)).toStrictEqual(expected);
+  });
+  test('with negative delays', () => {
+    const testData = [
+      {
+        duration: -20,
+        type: 'delay',
+        id: '24240',
+      },
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 100,
+        timeEnd: 200,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    const expected = [
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 80,
+        timeEnd: 180,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    expect(getEventsWithDelay(testData)).toStrictEqual(expected);
+  });
 });
 
 describe('getEventsWithDelay edge cases', () => {
+  it('ensures time start cannot be below 0', () => {
+    const testData = [
+      {
+        duration: -200,
+        type: 'delay',
+        id: '24240',
+      },
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 10,
+        timeEnd: 20,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    const expected = [
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 0,
+        timeEnd: 0,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    expect(getEventsWithDelay(testData)).toStrictEqual(expected);
+  });
+  it('does not modify original array', () => {
+    const testData = [
+      {
+        duration: 10,
+        type: 'delay',
+        id: '24240',
+      },
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 10,
+        timeEnd: 20,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    const expected = [
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 20,
+        timeEnd: 30,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    const expectedSafe = [
+      {
+        title: 'Welcome to Ontime',
+        timeStart: 20,
+        timeEnd: 30,
+        colour: '',
+        type: 'event',
+        id: '5946',
+      },
+    ];
+
+    expect(getEventsWithDelay(testData)).toStrictEqual(expected);
+    expect(getEventsWithDelay(expectedSafe)).toStrictEqual(expected);
+  });
+
   it('given an empty array', () => {
     const emptyArray = {
       test: [],
diff --git a/apps/client/src/common/utils/eventsManager.ts b/apps/client/src/common/utils/eventsManager.ts
index 867060726..9f07ba48d 100644
--- a/apps/client/src/common/utils/eventsManager.ts
+++ b/apps/client/src/common/utils/eventsManager.ts
@@ -11,21 +11,27 @@ import { formatTime } from './time';
 export const getEventsWithDelay = (events: OntimeRundownEntry[]): OntimeEvent[] => {
   if (events == null) return [];
 
-  const unfilteredEvents = [...events];
+  const delayedEvents: OntimeEvent[] = [];
 
   // Add running delay
   let delay = 0;
-  for (const event of unfilteredEvents) {
+  for (const event of events) {
     if (event.type === SupportedEvent.Block) delay = 0;
-    else if (event.type === SupportedEvent.Delay) delay = delay + event.duration;
-    else if (event.type === SupportedEvent.Event && delay > 0) {
-      event.timeStart += delay;
-      event.timeEnd += delay;
+    else if (event.type === SupportedEvent.Delay) {
+      if (typeof event.duration === 'number') {
+        delay += event.duration;
+      }
+    } else if (event.type === SupportedEvent.Event) {
+      const delayedEvent = { ...event };
+      if (delay !== 0) {
+        delayedEvent.timeStart = Math.max(delayedEvent.timeStart + delay, 0);
+        delayedEvent.timeEnd = Math.max(delayedEvent.timeEnd + delay, 0);
+      }
+      delayedEvents.push(delayedEvent);
     }
   }
 
-  // filter just events
-  return unfilteredEvents.filter((event) => event.type === SupportedEvent.Event) as OntimeEvent[];
+  return delayedEvents;
 };
 
 /**
@@ -57,7 +63,7 @@ export const trimEventlist = (events: OntimeRundownEntry[], selectedId: string,
 
 type FormatEventListOptionsProp = {
   showEnd?: boolean;
-}
+};
 /**
  * @description Returns list of events formatted to be displayed
  * @param {Object[]} events - given events
@@ -67,7 +73,12 @@ type FormatEventListOptionsProp = {
  * @param {boolean} [options.showEnd] - whether to show the end time
  * @returns {Object[]} Formatted list of events [{time: -, title: -, isNow, isNext}]
  */
-export const formatEventList = (events: OntimeEvent[], selectedId: string, nextId: string, options: FormatEventListOptionsProp) => {
+export const formatEventList = (
+  events: OntimeEvent[],
+  selectedId: string,
+  nextId: string,
+  options: FormatEventListOptionsProp,
+) => {
   if (events == null) return [];
   const { showEnd = false } = options;
 
diff --git a/apps/client/src/common/utils/time.ts b/apps/client/src/common/utils/time.ts
index e24b8f8f6..269c07a12 100644
--- a/apps/client/src/common/utils/time.ts
+++ b/apps/client/src/common/utils/time.ts
@@ -46,7 +46,7 @@ type FormatOptions = {
  * @param {function} resolver
  * @return {string}
  */
-export const formatTime = (milliseconds: number | null, options: FormatOptions, resolver = resolveTimeFormat) => {
+export const formatTime = (milliseconds: number | null, options?: FormatOptions, resolver = resolveTimeFormat) => {
   if (milliseconds === null) {
     return '...';
   }