diff --git a/src/constant.js b/src/constant.js
index 22d6e8adc..08e91a6a6 100644
--- a/src/constant.js
+++ b/src/constant.js
@@ -27,4 +27,4 @@ export const INVALID_DATE_STRING = 'Invalid Date'
 
 // regex
 export const REGEX_PARSE = /^(\d{4})[-/]?(\d{1,2})?[-/]?(\d{0,2})[Tt\s]*(\d{1,2})?:?(\d{1,2})?:?(\d{1,2})?[.:]?(\d+)?$/
-export const REGEX_FORMAT = /\[([^\]]+)]|Y{1,4}|M{1,4}|D{1,2}|d{1,4}|H{1,2}|h{1,2}|a|A|m{1,2}|s{1,2}|Z{1,2}|SSS/g
+export const REGEX_FORMAT = /\[([^\]]+)]|Y{1,4}|M{1,4}|D{1,2}|d{1,4}|H{1,2}|h{1,2}|a|A|m{1,2}|s{1,2}|Z{1,2}|S{1,3}/g
diff --git a/src/index.js b/src/index.js
index 061ade178..91682e1f6 100644
--- a/src/index.js
+++ b/src/index.js
@@ -328,6 +328,10 @@ class Dayjs {
           return String(this.$s)
         case 'ss':
           return Utils.s(this.$s, 2, '0')
+        case 'S':
+          return String(Math.round(this.$ms / 100))
+        case 'SS':
+          return Utils.s(Math.round(this.$ms / 10), 2, '0')
         case 'SSS':
           return Utils.s(this.$ms, 3, '0')
         case 'Z':
diff --git a/src/plugin/customParseFormat/index.js b/src/plugin/customParseFormat/index.js
index c7082833c..6d1bdb802 100644
--- a/src/plugin/customParseFormat/index.js
+++ b/src/plugin/customParseFormat/index.js
@@ -1,6 +1,6 @@
 import { u } from '../localizedFormat/utils'
 
-const formattingTokens = /(\[[^[]*\])|([-_:/.,()\s]+)|(A|a|Q|YYYY|YY?|ww?|MM?M?M?|Do|DD?|hh?|HH?|mm?|ss?|S{1,3}|z|ZZ?)/g
+const formattingTokens = /(\[[^[]*\])|([-_:/.,()\s]+)|(A|a|Q|YYYY|YY?|ww?|MM?M?M?|Do|DD?|hh?|HH?|mm?|ss?|SS?S?|z|ZZ?)/g
 
 const match1 = /\d/ // 0 - 9
 const match2 = /\d\d/ // 00 - 99
diff --git a/src/plugin/duration/index.js b/src/plugin/duration/index.js
index e2060c344..e3d8de378 100644
--- a/src/plugin/duration/index.js
+++ b/src/plugin/duration/index.js
@@ -180,6 +180,8 @@ class Duration {
       mm: $u.s(this.$d.minutes, 2, '0'),
       s: this.$d.seconds,
       ss: $u.s(this.$d.seconds, 2, '0'),
+      S: String(Math.round(this.$d.milliseconds / 100)),
+      SS: $u.s(Math.round(this.$d.milliseconds / 10), 2, '0'),
       SSS: $u.s(this.$d.milliseconds, 3, '0')
     }
     return str.replace(REGEX_FORMAT, (match, $1) => $1 || String(matches[match]))
diff --git a/test/plugin/customParseFormat.test.js b/test/plugin/customParseFormat.test.js
index fb4030176..dffabfe38 100644
--- a/test/plugin/customParseFormat.test.js
+++ b/test/plugin/customParseFormat.test.js
@@ -460,3 +460,21 @@ it('parse w, ww', () => {
   const format2 = 'YYYY-[w]ww'
   expect(dayjs(input2, format2).format(format1)).toBe(input2)
 })
+
+describe('parse milliseconds', () => {
+  it('S', () => {
+    const input = '2024-01-01T00:00:00.1'
+    const format1 = 'YYYY-MM-DDTHH:mm:ss.S'
+    expect(dayjs(input, format1, true).format(format1)).toBe(input)
+  })
+  it('SS', () => {
+    const input = '2024-01-01T00:00:00.12'
+    const format1 = 'YYYY-MM-DDTHH:mm:ss.SS'
+    expect(dayjs(input, format1, true).format(format1)).toBe(input)
+  })
+  it('SSS', () => {
+    const input = '2024-01-01T00:00:00.123'
+    const format1 = 'YYYY-MM-DDTHH:mm:ss.SSS'
+    expect(dayjs(input, format1, true).format(format1)).toBe(input)
+  })
+})
diff --git a/test/plugin/duration.test.js b/test/plugin/duration.test.js
index 3e726af91..4ed572fc5 100644
--- a/test/plugin/duration.test.js
+++ b/test/plugin/duration.test.js
@@ -305,7 +305,7 @@ describe('Format', () => {
       .add(9, 'months')
       .add(2, 'years')
       .add(10, 'milliseconds')
-    expect(d.format('Y/YY.YYYYTESTM:MM:D:DD:H:HH:m:mm:s:ss:SSS'))
+    expect(d.format('Y/YY.YYYY[TEST]M:MM:D:DD:H:HH:m:mm:s:ss:SSS'))
       .toBe('2/02.0002TEST9:09:6:06:8:08:5:05:1:01:010')
   })
 })