diff --git a/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.test.ts b/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.test.ts
index 7e77c12a0bf73..d2040f8e63f3a 100644
--- a/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.test.ts
+++ b/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.test.ts
@@ -7,7 +7,7 @@
 
 import { random, mean } from 'lodash';
 import { SanitizedRule, AlertSummary } from '../types';
-import { IValidatedEvent } from '@kbn/event-log-plugin/server';
+import { IValidatedEvent, millisToNanos, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { EVENT_LOG_ACTIONS, EVENT_LOG_PROVIDER, LEGACY_EVENT_LOG_ACTIONS } from '../plugin';
 import { alertSummaryFromEventLog } from './alert_summary_from_event_log';
 
@@ -643,7 +643,7 @@ export class EventsFactory {
       event: {
         provider: EVENT_LOG_PROVIDER,
         action: EVENT_LOG_ACTIONS.execute,
-        duration: `${random(2000, 180000)}000000`,
+        duration: millisToNanos(random(2000, 180000)),
       },
     };
 
@@ -710,7 +710,7 @@ export class EventsFactory {
     return this.events
       .filter((ev) => ev?.event?.action === 'execute' && ev?.event?.duration !== undefined)
       .reduce((res: Record<string, number>, ev) => {
-        res[ev?.['@timestamp']!] = Number(BigInt(ev?.event?.duration!) / BigInt(1000 * 1000));
+        res[ev?.['@timestamp']!] = nanosToMillis(ev?.event?.duration!);
         return res;
       }, {});
   }
diff --git a/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.ts b/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.ts
index 25f5cdf1abf04..54ac23bf94f2a 100644
--- a/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.ts
+++ b/x-pack/plugins/alerting/server/lib/alert_summary_from_event_log.ts
@@ -6,12 +6,10 @@
  */
 
 import { mean } from 'lodash';
-import { IEvent } from '@kbn/event-log-plugin/server';
+import { IEvent, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { SanitizedRule, AlertSummary, AlertStatus } from '../types';
 import { EVENT_LOG_ACTIONS, EVENT_LOG_PROVIDER, LEGACY_EVENT_LOG_ACTIONS } from '../plugin';
 
-const Millis2Nanos = BigInt(1000 * 1000);
-
 export interface AlertSummaryFromEventLogParams {
   rule: SanitizedRule<{ bar: boolean }>;
   events: IEvent[];
@@ -111,7 +109,7 @@ export function alertSummaryFromEventLog(params: AlertSummaryFromEventLogParams)
     }
 
     if (event?.event?.duration) {
-      const eventDirationMillis = Number(BigInt(event.event.duration) / Millis2Nanos);
+      const eventDirationMillis = nanosToMillis(event.event.duration);
       eventDurations.push(eventDirationMillis);
       eventDurationsWithTimestamp[event['@timestamp']!] = eventDirationMillis;
     }
diff --git a/x-pack/plugins/alerting/server/task_runner/task_runner.ts b/x-pack/plugins/alerting/server/task_runner/task_runner.ts
index 50a387cda1cd5..afed1f4c9ad09 100644
--- a/x-pack/plugins/alerting/server/task_runner/task_runner.ts
+++ b/x-pack/plugins/alerting/server/task_runner/task_runner.ts
@@ -12,7 +12,12 @@ import uuid from 'uuid';
 import { addSpaceIdToPath } from '@kbn/spaces-plugin/server';
 import { KibanaRequest, Logger } from '@kbn/core/server';
 import { ConcreteTaskInstance, throwUnrecoverableError } from '@kbn/task-manager-plugin/server';
-import { IEvent, SAVED_OBJECT_REL_PRIMARY } from '@kbn/event-log-plugin/server';
+import {
+  IEvent,
+  SAVED_OBJECT_REL_PRIMARY,
+  millisToNanos,
+  nanosToMillis,
+} from '@kbn/event-log-plugin/server';
 import { TaskRunnerContext } from './task_runner_factory';
 import { createExecutionHandler, ExecutionHandler } from './create_execution_handler';
 import { Alert, createAlertFactory } from '../alert';
@@ -803,9 +808,7 @@ export class TaskRunner<
 
     // Copy duration into execution status if available
     if (null != event.event?.duration) {
-      executionStatus.lastDuration = Math.round(
-        Number(BigInt(event.event?.duration) / BigInt(Millis2Nanos))
-      );
+      executionStatus.lastDuration = nanosToMillis(event.event?.duration);
       monitoringHistory.duration = executionStatus.lastDuration;
     }
 
@@ -1066,8 +1069,7 @@ function trackAlertDurations<
       : currentAlerts[id].getState();
     const durationInMs =
       new Date(currentTime).valueOf() - new Date(state.start as string).valueOf();
-    const durationInNanoStr = durationInMs !== 0 ? `${durationInMs}000000` : '0';
-    const duration = state.start ? durationInNanoStr : undefined;
+    const duration = state.start ? millisToNanos(durationInMs) : undefined;
     currentAlerts[id].replaceState({
       ...state,
       ...(state.start ? { start: state.start } : {}),
@@ -1080,8 +1082,7 @@ function trackAlertDurations<
     const state = recoveredAlerts[id].getState();
     const durationInMs =
       new Date(currentTime).valueOf() - new Date(state.start as string).valueOf();
-    const durationInNanoStr = durationInMs !== 0 ? `${durationInMs}000000` : '0';
-    const duration = state.start ? durationInNanoStr : undefined;
+    const duration = state.start ? millisToNanos(durationInMs) : undefined;
     recoveredAlerts[id].replaceState({
       ...state,
       ...(duration ? { duration } : {}),
diff --git a/x-pack/plugins/event_log/common/lib/nanos_to_millis.test.ts b/x-pack/plugins/event_log/common/lib/nanos_to_millis.test.ts
index 52ad3ceb6e090..3a04c57b9edbf 100644
--- a/x-pack/plugins/event_log/common/lib/nanos_to_millis.test.ts
+++ b/x-pack/plugins/event_log/common/lib/nanos_to_millis.test.ts
@@ -23,4 +23,10 @@ describe('nanosToMillis', () => {
   test('should return 9007199254740991 (Number.MAX_SAFE_INTEGER) when passing in "9007199254740991000000" nanos', () => {
     expect(nanosToMillis('9007199254740991000000')).toEqual(9007199254740991);
   });
+
+  test('should work when numbers are passed in', () => {
+    expect(nanosToMillis(0)).toEqual(0);
+    expect(nanosToMillis(1)).toEqual(0);
+    expect(nanosToMillis(1000001)).toEqual(1);
+  });
 });
diff --git a/x-pack/plugins/event_log/common/lib/nanos_to_millis.ts b/x-pack/plugins/event_log/common/lib/nanos_to_millis.ts
index 5a9a73cd956d7..a0512fb528a91 100644
--- a/x-pack/plugins/event_log/common/lib/nanos_to_millis.ts
+++ b/x-pack/plugins/event_log/common/lib/nanos_to_millis.ts
@@ -7,6 +7,6 @@
 
 const ONE_MILLION = BigInt(1000 * 1000);
 
-export function nanosToMillis(nanos: string): number {
+export function nanosToMillis(nanos: string | number): number {
   return Number(BigInt(nanos) / ONE_MILLION);
 }
diff --git a/x-pack/plugins/event_log/server/event_logger.test.ts b/x-pack/plugins/event_log/server/event_logger.test.ts
index 0836001ee5fbf..f1f849bd3b17b 100644
--- a/x-pack/plugins/event_log/server/event_logger.test.ts
+++ b/x-pack/plugins/event_log/server/event_logger.test.ts
@@ -5,6 +5,7 @@
  * 2.0.
  */
 
+import { nanosToMillis } from '../common';
 import { IEvent, IEventLogger, IEventLogService } from '.';
 import { ECS_VERSION } from './types';
 import { EventLogService } from './event_log_service';
@@ -137,9 +138,9 @@ describe('EventLogger', () => {
 
     expect(timeStopValue).toBeGreaterThanOrEqual(timeStartValue);
 
-    const duration = BigInt(event.event!.duration!);
+    const duration = Number(event.event!.duration!);
     expect(duration).toBeGreaterThan(0.95 * delayMS * 1000 * 1000);
-    expect(Number(duration / BigInt(1000 * 1000))).toBeCloseTo(timeStopValue - timeStartValue);
+    expect(nanosToMillis(duration)).toBeCloseTo(timeStopValue - timeStartValue);
   });
 
   test('timing method endTiming() method works when startTiming() is not called', async () => {
diff --git a/x-pack/plugins/event_log/server/index.ts b/x-pack/plugins/event_log/server/index.ts
index c69d7780a6204..cd386483fef8f 100644
--- a/x-pack/plugins/event_log/server/index.ts
+++ b/x-pack/plugins/event_log/server/index.ts
@@ -9,6 +9,8 @@ import { PluginInitializerContext, PluginConfigDescriptor } from '@kbn/core/serv
 import { ConfigSchema, IEventLogConfig } from './types';
 import { Plugin } from './plugin';
 
+export { millisToNanos, nanosToMillis } from '../common';
+
 export type {
   IEventLogService,
   IEventLogger,
diff --git a/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/execute.ts b/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/execute.ts
index 025c28d39c1aa..c8433ac60575f 100644
--- a/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/execute.ts
+++ b/x-pack/test/alerting_api_integration/security_and_spaces/tests/actions/execute.ts
@@ -6,7 +6,7 @@
  */
 
 import expect from '@kbn/expect';
-import { IValidatedEvent } from '@kbn/event-log-plugin/server';
+import { IValidatedEvent, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { UserAtSpaceScenarios } from '../../scenarios';
 import {
   ESTestIndexTool,
@@ -17,8 +17,6 @@ import {
 } from '../../../common/lib';
 import { FtrProviderContext } from '../../../common/ftr_provider_context';
 
-const NANOS_IN_MILLIS = BigInt(1000 * 1000);
-
 // eslint-disable-next-line import/no-default-export
 export default function ({ getService }: FtrProviderContext) {
   const supertest = getService('supertest');
@@ -543,10 +541,7 @@ export default function ({ getService }: FtrProviderContext) {
     expect(startExecuteEventStart).to.equal(executeEventStart);
     expect(executeEventEnd).to.be.ok();
 
-    const durationDiff = Math.abs(
-      Math.round(Number(BigInt(duration!) / NANOS_IN_MILLIS)) -
-        (executeEventEnd - executeEventStart)
-    );
+    const durationDiff = Math.abs(nanosToMillis(duration!) - (executeEventEnd - executeEventStart));
 
     // account for rounding errors
     expect(durationDiff < 1).to.equal(true);
diff --git a/x-pack/test/alerting_api_integration/security_and_spaces/tests/alerting/alerts.ts b/x-pack/test/alerting_api_integration/security_and_spaces/tests/alerting/alerts.ts
index 926d01ca38c48..407d6467296e4 100644
--- a/x-pack/test/alerting_api_integration/security_and_spaces/tests/alerting/alerts.ts
+++ b/x-pack/test/alerting_api_integration/security_and_spaces/tests/alerting/alerts.ts
@@ -8,7 +8,7 @@
 import expect from '@kbn/expect';
 import { omit } from 'lodash';
 import type * as estypes from '@elastic/elasticsearch/lib/api/typesWithBodyKey';
-import { IValidatedEvent } from '@kbn/event-log-plugin/server';
+import { IValidatedEvent, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { TaskRunning, TaskRunningStage } from '@kbn/task-manager-plugin/server/task_running';
 import { ConcreteTaskInstance } from '@kbn/task-manager-plugin/server';
 import { UserAtSpaceScenarios, Superuser } from '../../scenarios';
@@ -25,8 +25,6 @@ import {
   getEventLog,
 } from '../../../common/lib';
 
-const NANOS_IN_MILLIS = BigInt(1000 * 1000);
-
 // eslint-disable-next-line import/no-default-export
 export default function alertTests({ getService }: FtrProviderContext) {
   const supertest = getService('supertest');
@@ -1307,9 +1305,7 @@ instanceStateValue: true
     expect(eventStart).to.be.ok();
     expect(eventEnd).to.be.ok();
 
-    const durationDiff = Math.abs(
-      Math.round(Number(BigInt(duration!) / NANOS_IN_MILLIS)) - (eventEnd - eventStart)
-    );
+    const durationDiff = Math.abs(nanosToMillis(duration!) - (eventEnd - eventStart));
 
     // account for rounding errors
     expect(durationDiff < 1).to.equal(true);
diff --git a/x-pack/test/alerting_api_integration/spaces_only/tests/actions/execute.ts b/x-pack/test/alerting_api_integration/spaces_only/tests/actions/execute.ts
index 444c4a634697f..24c6427fdf2f6 100644
--- a/x-pack/test/alerting_api_integration/spaces_only/tests/actions/execute.ts
+++ b/x-pack/test/alerting_api_integration/spaces_only/tests/actions/execute.ts
@@ -6,7 +6,7 @@
  */
 import type { Client } from '@elastic/elasticsearch';
 import expect from '@kbn/expect';
-import { IValidatedEvent } from '@kbn/event-log-plugin/server';
+import { IValidatedEvent, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { Spaces } from '../../scenarios';
 import {
   ESTestIndexTool,
@@ -17,8 +17,6 @@ import {
 } from '../../../common/lib';
 import { FtrProviderContext } from '../../../common/ftr_provider_context';
 
-const NANOS_IN_MILLIS = BigInt(1000 * 1000);
-
 // eslint-disable-next-line import/no-default-export
 export default function ({ getService }: FtrProviderContext) {
   const supertest = getService('supertest');
@@ -377,10 +375,7 @@ export default function ({ getService }: FtrProviderContext) {
     expect(startExecuteEventStart).to.equal(executeEventStart);
     expect(executeEventEnd).to.be.ok();
 
-    const durationDiff = Math.abs(
-      Math.round(Number(BigInt(duration!) / NANOS_IN_MILLIS)) -
-        (executeEventEnd - executeEventStart)
-    );
+    const durationDiff = Math.abs(nanosToMillis(duration!) - (executeEventEnd - executeEventStart));
 
     // account for rounding errors
     expect(durationDiff < 1).to.equal(true);
diff --git a/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log.ts b/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log.ts
index c8905034ce8db..bc382e5d733dd 100644
--- a/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log.ts
+++ b/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log.ts
@@ -7,7 +7,7 @@
 
 import expect from '@kbn/expect';
 import uuid from 'uuid';
-import { IValidatedEvent } from '@kbn/event-log-plugin/server';
+import { IValidatedEvent, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { Spaces } from '../../scenarios';
 import {
   getUrlPrefix,
@@ -18,8 +18,6 @@ import {
 } from '../../../common/lib';
 import { FtrProviderContext } from '../../../common/ftr_provider_context';
 
-const NANOS_IN_MILLIS = BigInt(1000 * 1000);
-
 // eslint-disable-next-line import/no-default-export
 export default function eventLogTests({ getService }: FtrProviderContext) {
   const supertest = getService('supertest');
@@ -869,9 +867,7 @@ export function validateEvent(event: IValidatedEvent, params: ValidateEventLogPa
     if (shouldHaveEventEnd !== false) {
       expect(eventEnd).to.be.ok();
 
-      const durationDiff = Math.abs(
-        Math.round(Number(BigInt(duration!) / NANOS_IN_MILLIS)) - (eventEnd - eventStart)
-      );
+      const durationDiff = Math.abs(nanosToMillis(duration!) - (eventEnd - eventStart));
 
       // account for rounding errors
       expect(durationDiff < 1).to.equal(true);
diff --git a/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log_alerts.ts b/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log_alerts.ts
index c752af980013b..46da0e597e66a 100644
--- a/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log_alerts.ts
+++ b/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/event_log_alerts.ts
@@ -6,7 +6,7 @@
  */
 
 import expect from '@kbn/expect';
-import { IValidatedEvent } from '@kbn/event-log-plugin/server';
+import { IValidatedEvent, nanosToMillis } from '@kbn/event-log-plugin/server';
 import { Spaces } from '../../scenarios';
 import { getUrlPrefix, getTestRuleData, ObjectRemover, getEventLog } from '../../../common/lib';
 import { FtrProviderContext } from '../../../common/ftr_provider_context';
@@ -126,7 +126,7 @@ export default function eventLogAlertTests({ getService }: FtrProviderContext) {
             expect(
               new Date(instanceEvents[i]?.event?.end!).valueOf() -
                 new Date(instanceEvents[i]?.event?.start!).valueOf()
-            ).to.equal(Number(BigInt(instanceEvents[i]?.event?.duration!) / BigInt(1000000)));
+            ).to.equal(nanosToMillis(instanceEvents[i]?.event?.duration!));
             break;
         }
       }