From 70c123990dcc6bd479fa2b5d7f9985127872a826 Mon Sep 17 00:00:00 2001
From: dyoshikawa <34151621+dyoshikawa@users.noreply.github.com>
Date: Wed, 29 Jul 2020 11:42:13 +0900
Subject: [PATCH] fix: Update Regex to parse 'YYYY' correctly (#969)

---
 src/constant.js         | 2 +-
 src/index.js            | 6 ++++--
 test/plugin/utc.test.js | 9 +++++++--
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/constant.js b/src/constant.js
index 5dbff805..b253c74e 100644
--- a/src/constant.js
+++ b/src/constant.js
@@ -26,5 +26,5 @@ export const FORMAT_DEFAULT = 'YYYY-MM-DDTHH:mm:ssZ'
 export const INVALID_DATE_STRING = 'Invalid Date'
 
 // regex
-export const REGEX_PARSE = /^(\d{4})-?(\d{1,2})-?(\d{0,2})[^0-9]*(\d{1,2})?:?(\d{1,2})?:?(\d{1,2})?.?(\d{1,3})?$/
+export const REGEX_PARSE = /^(\d{4})-?(\d{1,2})?-?(\d{0,2})[^0-9]*(\d{1,2})?:?(\d{1,2})?:?(\d{1,2})?.?(\d{1,3})?$/
 export const REGEX_FORMAT = /\[([^\]]+)]|Y{2,4}|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
diff --git a/src/index.js b/src/index.js
index abda8c9e..9a669e6b 100644
--- a/src/index.js
+++ b/src/index.js
@@ -59,11 +59,13 @@ const parseDate = (cfg) => {
   if (typeof date === 'string' && !/Z$/i.test(date)) {
     const d = date.match(C.REGEX_PARSE)
     if (d) {
+      const m = d[2] - 1 || 0
       if (utc) {
-        return new Date(Date.UTC(d[1], d[2] - 1, d[3]
+        return new Date(Date.UTC(d[1], m, d[3]
           || 1, d[4] || 0, d[5] || 0, d[6] || 0, d[7] || 0))
       }
-      return new Date(d[1], d[2] - 1, d[3] || 1, d[4] || 0, d[5] || 0, d[6] || 0, d[7] || 0)
+      return new Date(d[1], m, d[3]
+          || 1, d[4] || 0, d[5] || 0, d[6] || 0, d[7] || 0)
     }
   }
 
diff --git a/test/plugin/utc.test.js b/test/plugin/utc.test.js
index 9a90adca..dc290de1 100644
--- a/test/plugin/utc.test.js
+++ b/test/plugin/utc.test.js
@@ -56,12 +56,17 @@ describe('Parse UTC ', () => {
 
   it('Parse date string without timezome', () => {
     const d = '2018-09-06'
-    const d2 = '2018-09'
     expect(dayjs.utc(d).format()).toEqual(moment.utc(d).format())
     expect(dayjs.utc(d).format()).toEqual('2018-09-06T00:00:00Z')
+    expect(dayjs(d).utc().format()).toEqual(moment(d).utc().format())
+    const d2 = '2018-09'
     expect(dayjs.utc(d2).format()).toEqual(moment.utc(d2).format())
     expect(dayjs.utc(d2).format()).toEqual('2018-09-01T00:00:00Z')
-    expect(dayjs(d).utc().format()).toEqual(moment(d).utc().format())
+    expect(dayjs(d2).utc().format()).toEqual(moment(d2).utc().format())
+    const d3 = '2018'
+    expect(dayjs.utc(d3).format()).toEqual(moment.utc(d3).format())
+    expect(dayjs.utc(d3).format()).toEqual('2018-01-01T00:00:00Z')
+    expect(dayjs(d3).utc().format()).toEqual(moment(d3).utc().format())
   })
 
   it('creating with utc with timezone', () => {