diff --git a/src/plugins/discover/public/application/angular/context/api/utils/date_conversion.ts b/src/plugins/discover/public/application/angular/context/api/utils/date_conversion.ts
index 64544a335c911..4369234a3ce9a 100644
--- a/src/plugins/discover/public/application/angular/context/api/utils/date_conversion.ts
+++ b/src/plugins/discover/public/application/angular/context/api/utils/date_conversion.ts
@@ -31,15 +31,6 @@ export function extractNanos(timeFieldValue: string = ''): string {
   return fractionSeconds.length !== 9 ? fractionSeconds.padEnd(9, '0') : fractionSeconds;
 }
 
-/**
- * extract the nanoseconds as string of a given ISO formatted timestamp
- */
-export function convertIsoToNanosAsStr(isoValue: string): string {
-  const nanos = extractNanos(isoValue);
-  const millis = convertIsoToMillis(isoValue);
-  return `${millis}${nanos.substr(3, 6)}`;
-}
-
 /**
  * convert an iso formatted string to number of milliseconds since
  * 1970-01-01T00:00:00.000Z
diff --git a/src/plugins/discover/public/application/angular/context/api/utils/get_es_query_search_after.ts b/src/plugins/discover/public/application/angular/context/api/utils/get_es_query_search_after.ts
index d4ee9e0e0f287..24ac19a7e3bc3 100644
--- a/src/plugins/discover/public/application/angular/context/api/utils/get_es_query_search_after.ts
+++ b/src/plugins/discover/public/application/angular/context/api/utils/get_es_query_search_after.ts
@@ -16,7 +16,6 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-import { convertIsoToNanosAsStr } from './date_conversion';
 import { SurrDocType, EsHitRecordList, EsHitRecord } from '../context';
 
 export type EsQuerySearchAfter = [string | number, string | number];
@@ -38,15 +37,10 @@ export function getEsQuerySearchAfter(
     // already surrounding docs -> first or last record  is used
     const afterTimeRecIdx = type === 'successors' && documents.length ? documents.length - 1 : 0;
     const afterTimeDoc = documents[afterTimeRecIdx];
-    const afterTimeValue = nanoSeconds
-      ? convertIsoToNanosAsStr(afterTimeDoc.fields[timeFieldName][0])
-      : afterTimeDoc.sort[0];
+    const afterTimeValue = nanoSeconds ? afterTimeDoc._source[timeFieldName] : afterTimeDoc.sort[0];
     return [afterTimeValue, afterTimeDoc.sort[1]];
   }
   // if data_nanos adapt timestamp value for sorting, since numeric value was rounded by browser
   // ES search_after also works when number is provided as string
-  return [
-    nanoSeconds ? convertIsoToNanosAsStr(anchor.fields[timeFieldName][0]) : anchor.sort[0],
-    anchor.sort[1],
-  ];
+  return [nanoSeconds ? anchor._source[timeFieldName] : anchor.sort[0], anchor.sort[1]];
 }
diff --git a/test/functional/apps/context/_date_nanos.js b/test/functional/apps/context/_date_nanos.js
index 89769caaea253..cdf2d6c04be83 100644
--- a/test/functional/apps/context/_date_nanos.js
+++ b/test/functional/apps/context/_date_nanos.js
@@ -30,8 +30,7 @@ export default function ({ getService, getPageObjects }) {
   const PageObjects = getPageObjects(['common', 'context', 'timePicker', 'discover']);
   const esArchiver = getService('esArchiver');
 
-  // FLAKY/FAILING ES PROMOTION: https://github.com/elastic/kibana/issues/58815
-  describe.skip('context view for date_nanos', () => {
+  describe('context view for date_nanos', () => {
     before(async function () {
       await security.testUser.setRoles(['kibana_admin', 'kibana_date_nanos']);
       await esArchiver.loadIfNeeded('date_nanos');
diff --git a/test/functional/apps/context/_date_nanos_custom_timestamp.js b/test/functional/apps/context/_date_nanos_custom_timestamp.js
index 6329f6c431e6a..8fe08d13af0aa 100644
--- a/test/functional/apps/context/_date_nanos_custom_timestamp.js
+++ b/test/functional/apps/context/_date_nanos_custom_timestamp.js
@@ -30,10 +30,7 @@ export default function ({ getService, getPageObjects }) {
   const PageObjects = getPageObjects(['common', 'context', 'timePicker', 'discover']);
   const esArchiver = getService('esArchiver');
 
-  // skipped due to a recent change in ES that caused search_after queries with data containing
-  // custom timestamp formats like in the testdata to fail
-  // https://github.com/elastic/kibana/issues/58815
-  describe.skip('context view for date_nanos with custom timestamp', () => {
+  describe('context view for date_nanos with custom timestamp', () => {
     before(async function () {
       await security.testUser.setRoles(['kibana_admin', 'kibana_date_nanos_custom']);
       await esArchiver.loadIfNeeded('date_nanos_custom');