From e242626dc94d1dd9c5b19caa3bd6fd88c4b3ca8e Mon Sep 17 00:00:00 2001
From: Mike Greiling <mike@pixelcog.com>
Date: Mon, 20 Sep 2021 14:55:03 -0600
Subject: [PATCH] Fix broken timezone abbreviations and GMT fallback

---
 src/dateformat.js    | 24 +++++++++++++++++-----
 test/test_mask-z_.js | 47 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 5 deletions(-)
 create mode 100644 test/test_mask-z_.js

diff --git a/src/dateformat.js b/src/dateformat.js
index 1f7e9e3..8b742f8 100644
--- a/src/dateformat.js
+++ b/src/dateformat.js
@@ -14,7 +14,7 @@
 
 // Regexes and supporting functions are cached through closure
 const token = /d{1,4}|D{3,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|W{1,2}|[LlopSZN]|"[^"]*"|'[^']*'/g;
-const timezone = /\b((?:[PMCEA][SDP][TC])(?:[-+]\d{4})?|(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time)\b/g;
+const timezone = /\b(?:[A-Z]{1,3}[A-Z][TC])(?:[-+]\d{4})?|((?:Australian )?(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time)\b/g;
 const timezoneClip = /[^-+\dA-Z]/g;
 
 /**
@@ -128,10 +128,7 @@ export default function dateFormat (date, mask, utc, gmt) {
         ? "GMT"
         : utc
           ? "UTC"
-          : (String(date).match(timezone) || [""])
-            .pop()
-            .replace(timezoneClip, "")
-            .replace(/GMT\+0000/g, "UTC"),
+          : formatTimezone(date),
     o: () =>
       (o() > 0 ? "-" : "+") +
       pad(Math.floor(Math.abs(o()) / 60) * 100 + (Math.abs(o()) % 60), 4),
@@ -310,3 +307,20 @@ const getDayOfWeek = (date) => {
   }
   return dow;
 };
+
+/**
+ * Get proper timezone abbreviation or timezone offset.
+ * 
+ * This will fall back to `GMT+xxxx` if it does not recognize the
+ * timezone within the `timezone` RegEx above. Currently only common
+ * American and Australian timezone abbreviations are supported.
+ * 
+ * @param  {String | Date} date
+ * @return {String}
+ */
+export const formatTimezone = (date) => {
+  return (String(date).match(timezone) || [""])
+    .pop()
+    .replace(timezoneClip, "")
+    .replace(/GMT\+0000/g, "UTC");
+};
diff --git a/test/test_mask-z_.js b/test/test_mask-z_.js
new file mode 100644
index 0000000..ea63700
--- /dev/null
+++ b/test/test_mask-z_.js
@@ -0,0 +1,47 @@
+import { strictEqual } from "node:assert";
+import { formatTimezone } from "../lib/dateformat.js";
+
+describe("Mask: 'Z'", function () {
+  it("should format 'Tue Sep 08 2020 13:26:11 GMT-0500 (Central Daylight Time)' as 'CDT'", function (done) {
+    var d = formatTimezone("Tue Sep 08 2020 13:26:11 GMT-0500 (Central Daylight Time)");
+    strictEqual(d, "CDT");
+    done();
+  });
+
+  it("should format 'Tue Sep 08 2020 12:26:11 GMT-0600 (Mountain Daylight Time)' as 'MDT'", function (done) {
+    var d = formatTimezone("Tue Sep 08 2020 12:26:11 GMT-0600 (Mountain Daylight Time)");
+    strictEqual(d, "MDT");
+    done();
+  });
+
+  it("should format 'Wed Sep 09 2020 04:28:21 GMT+1000 (Australian Eastern Standard Time)' as 'AEST'", function (done) {
+    var d = formatTimezone("Wed Sep 09 2020 04:28:21 GMT+1000 (Australian Eastern Standard Time)");
+    strictEqual(d, "AEST");
+    done();
+  });
+
+  it("should format 'Wed Sep 09 2020 03:56:05 GMT+0930 (Australian Central Standard Time)' as 'ACST'", function (done) {
+    var d = formatTimezone("Wed Sep 09 2020 03:56:05 GMT+0930 (Australian Central Standard Time)");
+    strictEqual(d, "ACST");
+    done();
+  });
+
+  it("should format 'Tue Feb 02 2021 09:51:33 GMT+1030 (Australian Central Daylight Time)' as 'ACDT'", function (done) {
+    var d = formatTimezone("Tue Feb 02 2021 09:51:33 GMT+1030 (Australian Central Daylight Time)");
+    strictEqual(d, "ACDT");
+    done();
+  });
+
+  /* Since CEST is not currently supported abbreviation we fall back to GMT+xxxx */
+  it("should format 'Tue Feb 02 2021 00:21:33 GMT+0100 (Central European Standard Time)' as 'GMT+0100' (fallback)", function (done) {
+    var d = formatTimezone("Tue Feb 02 2021 00:21:33 GMT+0100 (Central European Standard Time)");
+    strictEqual(d, "GMT+0100");
+    done();
+  });
+
+  it("should format 'Tue Sep 08 2020 20:26:22 GMT+0200 (Central European Summer Time)' as 'GMT+0200' (fallback)", function (done) {
+    var d = formatTimezone("Tue Sep 08 2020 20:26:22 GMT+0200 (Central European Summer Time)");
+    strictEqual(d, "GMT+0200");
+    done();
+  });
+});