From bbedc071fcdac12b4e05bcf76a49a261a1b67b01 Mon Sep 17 00:00:00 2001
From: lenamonj <lenamonj@yahoo.com>
Date: Wed, 29 Jul 2026 11:27:57 -0400
Subject: [PATCH] fix: parse fractional seconds shorter than 3 digits as a
 decimal fraction

---
 src/index.js       |  2 +-
 test/parse.test.js | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/index.js b/src/index.js
index 061ade178..d2634acad 100644
--- a/src/index.js
+++ b/src/index.js
@@ -69,7 +69,7 @@ const parseDate = (cfg) => {
     const d = date.match(C.REGEX_PARSE)
     if (d) {
       const m = d[2] - 1 || 0
-      const ms = (d[7] || '0').substring(0, 3)
+      const ms = `${d[7] || '0'}00`.substring(0, 3) // '.5' is 500ms: pad before truncating
       if (utc) {
         return new Date(Date.UTC(d[1], m, d[3]
           || 1, d[4] || 0, d[5] || 0, d[6] || 0, ms))
diff --git a/test/parse.test.js b/test/parse.test.js
index 9f2dedf2d..c649d78b6 100644
--- a/test/parse.test.js
+++ b/test/parse.test.js
@@ -89,6 +89,16 @@ describe('Parse', () => {
     expect(ds.millisecond()).toEqual(ms.millisecond())
   })
 
+  it('parses millisecond with fewer than 3 digits as a decimal fraction', () => {
+    const dates = ['2019-03-25T06:41:00.5', '2019-03-25T06:41:00.05', '2019-03-25T06:41:00.005']
+    dates.forEach((date) => {
+      const ds = dayjs(date)
+      const ms = moment(date)
+      expect(ds.valueOf()).toEqual(ms.valueOf())
+      expect(ds.millisecond()).toEqual(ms.millisecond())
+    })
+  })
+
   it('String Other, Undefined and Null and isValid', () => {
     global.console.warn = jest.genMockFunction()// moment.js otherString will throw warn
     expect(dayjs('otherString').toString().toLowerCase()).toBe(moment('otherString').toString().toLowerCase())