fix: pad millisecs to 3 digits

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').padEnd(3, '0').substring(0, 3)
       if (utc) {
         return new Date(Date.UTC(d[1], m, d[3]
           || 1, d[4] || 0, d[5] || 0, d[6] || 0, ms))

test/issues/issue1331.millisec-pad.test.js

@@ -0,0 +1,35 @@
+import dayjs from '../../src'
+
+describe('milliseconds padding bug (Issue #1331)', () => {
+  it('parses 2-digit milliseconds correctly (.52 should be 520ms not 52ms)', () => {
+    const timestamp = '2026-01-01T10:00:00.52'
+    const expected = new Date(timestamp).getTime()
+    const actual = dayjs(timestamp).valueOf()
+
+    expect(actual).toBe(expected)
+  })
+
+  it('parses 1-digit milliseconds correctly (.3 should be 300ms not 3ms)', () => {
+    const timestamp = '2026-01-01T10:00:00.3'
+    const expected = new Date(timestamp).getTime()
+    const actual = dayjs(timestamp).valueOf()
+
+    expect(actual).toBe(expected)
+  })
+
+  it('parses 3-digit milliseconds correctly (existing behavior)', () => {
+    const timestamp = '2026-01-01T10:00:00.620'
+    const expected = new Date(timestamp).getTime()
+    const actual = dayjs(timestamp).valueOf()
+
+    expect(actual).toBe(expected)
+  })
+
+  it('handles missing milliseconds', () => {
+    const timestamp = '2026-01-01T10:00:00'
+    const expected = new Date(timestamp).getTime()
+    const actual = dayjs(timestamp).valueOf()
+
+    expect(actual).toBe(expected)
+  })
+})