diff --git a/src/tools/date-time-converter/date-time-converter.e2e.spec.ts b/src/tools/date-time-converter/date-time-converter.e2e.spec.ts
index 34ee74951..249dd754e 100644
--- a/src/tools/date-time-converter/date-time-converter.e2e.spec.ts
+++ b/src/tools/date-time-converter/date-time-converter.e2e.spec.ts
@@ -29,5 +29,6 @@ test.describe('Date time converter - json to yaml', () => {
     expect((await page.getByTestId('Timestamp').inputValue()).trim()).toEqual('1681333824000');
     expect((await page.getByTestId('UTC format').inputValue()).trim()).toEqual('Wed, 12 Apr 2023 21:10:24 GMT');
     expect((await page.getByTestId('Mongo ObjectID').inputValue()).trim()).toEqual('64371e400000000000000000');
+    expect((await page.getByTestId('Excel date/time').inputValue()).trim()).toEqual('45028.88222222222');
   });
 });
diff --git a/src/tools/date-time-converter/date-time-converter.models.test.ts b/src/tools/date-time-converter/date-time-converter.models.test.ts
index 502cdc67b..c2c7bee99 100644
--- a/src/tools/date-time-converter/date-time-converter.models.test.ts
+++ b/src/tools/date-time-converter/date-time-converter.models.test.ts
@@ -1,5 +1,8 @@
 import { describe, expect, test } from 'vitest';
 import {
+  dateToExcelFormat,
+  excelFormatToDate,
+  isExcelFormat,
   isISO8601DateTimeString,
   isISO9075DateString,
   isMongoObjectId,
@@ -139,4 +142,39 @@ describe('date-time-converter models', () => {
       expect(isMongoObjectId('')).toBe(false);
     });
   });
+
+  describe('isExcelFormat', () => {
+    test('an Excel format string is a floating number that can be negative', () => {
+      expect(isExcelFormat('0')).toBe(true);
+      expect(isExcelFormat('1')).toBe(true);
+      expect(isExcelFormat('1.1')).toBe(true);
+      expect(isExcelFormat('-1.1')).toBe(true);
+      expect(isExcelFormat('-1')).toBe(true);
+
+      expect(isExcelFormat('')).toBe(false);
+      expect(isExcelFormat('foo')).toBe(false);
+      expect(isExcelFormat('1.1.1')).toBe(false);
+    });
+  });
+
+  describe('dateToExcelFormat', () => {
+    test('a date in Excel format is the number of days since 01/01/1900', () => {
+      expect(dateToExcelFormat(new Date('2016-05-20T00:00:00.000Z'))).toBe('42510');
+      expect(dateToExcelFormat(new Date('2016-05-20T12:00:00.000Z'))).toBe('42510.5');
+      expect(dateToExcelFormat(new Date('2023-10-31T09:26:06.421Z'))).toBe('45230.39312987268');
+      expect(dateToExcelFormat(new Date('1970-01-01T00:00:00.000Z'))).toBe('25569');
+      expect(dateToExcelFormat(new Date('1800-01-01T00:00:00.000Z'))).toBe('-36522');
+    });
+  });
+
+  describe('excelFormatToDate', () => {
+    test('a date in Excel format is the number of days since 01/01/1900', () => {
+      expect(excelFormatToDate('0')).toEqual(new Date('1899-12-30T00:00:00.000Z'));
+      expect(excelFormatToDate('1')).toEqual(new Date('1899-12-31T00:00:00.000Z'));
+      expect(excelFormatToDate('2')).toEqual(new Date('1900-01-01T00:00:00.000Z'));
+      expect(excelFormatToDate('4242.4242')).toEqual(new Date('1911-08-12T10:10:50.880Z'));
+      expect(excelFormatToDate('42738.22626859954')).toEqual(new Date('2017-01-03T05:25:49.607Z'));
+      expect(excelFormatToDate('-1000')).toEqual(new Date('1897-04-04T00:00:00.000Z'));
+    });
+  });
 });
diff --git a/src/tools/date-time-converter/date-time-converter.models.ts b/src/tools/date-time-converter/date-time-converter.models.ts
index 173b8a87a..f5eedbfa2 100644
--- a/src/tools/date-time-converter/date-time-converter.models.ts
+++ b/src/tools/date-time-converter/date-time-converter.models.ts
@@ -9,6 +9,9 @@ export {
   isTimestamp,
   isUTCDateString,
   isMongoObjectId,
+  dateToExcelFormat,
+  excelFormatToDate,
+  isExcelFormat,
 };
 
 const ISO8601_REGEX
@@ -21,6 +24,8 @@ const RFC3339_REGEX
 
 const RFC7231_REGEX = /^[A-Za-z]{3},\s[0-9]{2}\s[A-Za-z]{3}\s[0-9]{4}\s[0-9]{2}:[0-9]{2}:[0-9]{2}\sGMT$/;
 
+const EXCEL_FORMAT_REGEX = /^-?\d+(\.\d+)?$/;
+
 function createRegexMatcher(regex: RegExp) {
   return (date?: string) => !_.isNil(date) && regex.test(date);
 }
@@ -33,6 +38,8 @@ const isUnixTimestamp = createRegexMatcher(/^[0-9]{1,10}$/);
 const isTimestamp = createRegexMatcher(/^[0-9]{1,13}$/);
 const isMongoObjectId = createRegexMatcher(/^[0-9a-fA-F]{24}$/);
 
+const isExcelFormat = createRegexMatcher(EXCEL_FORMAT_REGEX);
+
 function isUTCDateString(date?: string) {
   if (_.isNil(date)) {
     return false;
@@ -45,3 +52,11 @@ function isUTCDateString(date?: string) {
     return false;
   }
 }
+
+function dateToExcelFormat(date: Date) {
+  return String(((date.getTime()) / (1000 * 60 * 60 * 24)) + 25569);
+}
+
+function excelFormatToDate(excelFormat: string | number) {
+  return new Date((Number(excelFormat) - 25569) * 86400 * 1000);
+}
diff --git a/src/tools/date-time-converter/date-time-converter.vue b/src/tools/date-time-converter/date-time-converter.vue
index 241c9cf6f..5636ed462 100644
--- a/src/tools/date-time-converter/date-time-converter.vue
+++ b/src/tools/date-time-converter/date-time-converter.vue
@@ -14,6 +14,9 @@ import {
 } from 'date-fns';
 import type { DateFormat, ToDateMapper } from './date-time-converter.types';
 import {
+  dateToExcelFormat,
+  excelFormatToDate,
+  isExcelFormat,
   isISO8601DateTimeString,
   isISO9075DateString,
   isMongoObjectId,
@@ -85,6 +88,12 @@ const formats: DateFormat[] = [
     toDate: objectId => new Date(Number.parseInt(objectId.substring(0, 8), 16) * 1000),
     formatMatcher: date => isMongoObjectId(date),
   },
+  {
+    name: 'Excel date/time',
+    fromDate: date => dateToExcelFormat(date),
+    toDate: excelFormatToDate,
+    formatMatcher: isExcelFormat,
+  },
 ];
 
 const formatIndex = ref(6);