1.3.2

README.md

@@ -9,17 +9,17 @@ XTZ is a poor man's `Temporal` polyfill, but just for time zones. \
 Demo: <https://therootcompany.github.io/tz.js/>
 
 ```js
-// What's the current time, in ISO format?
+// What's the current time, in ISO+Offset format?
 
 TZ.toLocalISOString(new Date()); // "2021-11-07T03:15:59.000-0500"
 TZ.timeZone(); // "America/New_York"
 ```
 
 ```js
-// What will the ISO datetime string be
+// What will the ISO+Offset datetime string be
 // when it's 3:15am in New York?
 //
-// (Relative New York time to Absolute UTC Time)
+// (Relative New York time to Absolute ISO+Offset Time)
 
 TZ.toOffsetISOString("2021-11-07 03:15:59.000", "America/New_York");
 // "2021-11-07T03:15:59.000-0500"
@@ -29,7 +29,7 @@ TZ.toOffsetISOString("2021-11-07 03:15:59.000", "America/New_York");
 // What time will it be in New York
 // when it's 7:15am UTC?
 //
-// (Absolute UTC time to Relative New York time)
+// (Absolute UTC Zulu time to Relative New York time)
 
 TZ.toTimeZoneISOString("2021-03-14T07:15:59.000Z", "America/New_York");
 // "2021-03-14T03:15:59.000-0400"
@@ -37,8 +37,8 @@ TZ.toTimeZoneISOString("2021-03-14T07:15:59.000Z", "America/New_York");
 
 # Features
 
-- [x] Translate a UTC time to a Time Zone
+- [x] Translate a UTC Zulu time to a Time Zone
-- [x] Translate a Zoned time to UTC
+- [x] Translate a Zoned time to ISO+Offset
 - [x] Handles **Daylight Savings**, Weird Time Zones, etc...
   - [x] Well-tested `npm run test`
 - [x] Lightweight (No deps)
@@ -93,7 +93,7 @@ https://www.youtube.com/playlist?list=PLxki0D-ilnqa6horOJ2G18WMZlJeQFlAt
 
 > Convert UTC into a Target Time Zone
 
-Use ISO timestamps representing the absolute UTC time (with or without offset):
+Use ISO timestamps representing the absolute UTC time (ISO with or without offset):
 
 ```txt
 "2021-11-07T08:15:59.000Z"
@@ -125,7 +125,7 @@ TZ.toTimeZoneISOString("2021-11-07T08:15:59.000Z", "America/New_York");
 var tzDate = TZ.toTimeZone("2021-11-07T08:15:59.000Z", "America/New_York");
 ```
 
-### You can also use a date object with an absolute UTC time:
+### You can also use a date object with an absolute ISO time:
 
 ```js
 var tzDate = TZ.toTimeZone(
@@ -148,7 +148,7 @@ new Date("2021-11-07T03:15:59.000-0500").toISOString());
 
 ## `fromTimeZone(dtString, timeZone)`
 
-> Convert a Target Time Zone into UTC
+> Convert a Target Time Zone into ISO
 
 Use ISO-like timestamps representing the _local_ time in the target time zone:
 

examples.js

@@ -22,9 +22,9 @@ var XTZ;
     console.info();
 
     console.info("\t// during daylight savings");
-    console.info(`\tXTZ.toUTC("2021-03-14 08:15:59.000", "America/New_York")`);
+    console.info(`\tXTZ.fromTimeZone("2021-03-14 08:15:59.000", "America/New_York")`);
     console.info(`\ttzDate.toISOString()`);
-    tzDate = XTZ.toUTC("2021-03-14 08:15:59.000", "America/New_York");
+    tzDate = XTZ.fromTimeZone("2021-03-14 08:15:59.000", "America/New_York");
     console.info(
       "\t" + tzDate.toISOString(),
       "// same as",
@@ -33,9 +33,9 @@ var XTZ;
     console.info();
 
     console.info("\t// during standard time");
-    console.info(`\tXTZ.toUTC("2021-11-07 08:15:59.000", "America/New_York")`);
+    console.info(`\tXTZ.fromTimeZone("2021-11-07 08:15:59.000", "America/New_York")`);
     console.info(`\ttzDate.toISOString()`);
-    tzDate = XTZ.toUTC("2021-11-07 08:15:59.000", "America/New_York");
+    tzDate = XTZ.fromTimeZone("2021-11-07 08:15:59.000", "America/New_York");
     console.info(
       "\t" + tzDate.toISOString(),
       "// same as",
@@ -65,9 +65,9 @@ var XTZ;
     console.info();
 
     console.info("\t// during standard time");
-    console.info(`\tXTZ.toUTC("2021-11-07T08:15:59.000Z", "America/New_York")`);
+    console.info(`\tXTZ.fromTimeZone("2021-11-07T08:15:59.000Z", "America/New_York")`);
     console.info(`\ttzDate.toISOString()`);
-    tzDate = XTZ.toUTC("2021-11-07T08:15:59.000Z", "America/New_York");
+    tzDate = XTZ.fromTimeZone("2021-11-07T08:15:59.000Z", "America/New_York");
     console.info(
       "\t" + tzDate.toISOString(),
       "// same as",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "xtz",
-  "version": "1.2.0",
+  "version": "1.3.2",
   "description": "A fast, lightweight, zero-dependency library to translate between Time Zones and UTC with native Intl.DateTimeFormat in ~100 LoC. For Node.js & Browsers.",
   "main": "xtz.js",
   "files": [

test.js

@@ -4,9 +4,10 @@ var TZ = require("./");
 
 function testUtcToTz(t) {
   var result = TZ.toTimeZone.apply(TZ, t.inputs).toISOString();
-  if (t.result !== result) {
+  var result2 = TZ.toTimeZoneISOString.apply(TZ, t.inputs);
+  if (result !== result2 || t.result !== result) {
     throw new Error(
-      `Invalid UTC to TZ conversion for ${t.desc}:\n` +
+      `Invalid UTC/ISO+Offset to TZ conversion for ${t.desc}:\n` +
         `\tExpected: ${t.result}\n` +
         `\tActual: ${result}\n`
     );
@@ -14,9 +15,11 @@ function testUtcToTz(t) {
 }
 
 function testTzToUtc(t) {
-  var result = TZ.toUTC.apply(TZ, t.inputs);
+  var result = TZ.fromTimeZone.apply(TZ, t.inputs).toISOString();
-  if (t.result !== result.toISOString()) {
+  var result2 = TZ.toOffsetISOString.apply(TZ, t.inputs);
-    console.log(result);
+  var result3 = TZ.toUTC.apply(TZ, t.inputs).toISOString();
+  if (t.result !== result || t.result !== result2 || t.result !== result3) {
+    console.error(result);
     throw new Error(
       `Invalid TZ to UTC conversion for ${t.desc}:\n` +
         `\tExpected: ${t.result}\n` +
@@ -44,23 +47,23 @@ function testTzToUtc(t) {
 
   // 12:15am NY -0500 => -0400
   {
-    desc: "UTC to 12:15am NY EST",
+    desc: "UTC Zulu to 12:15am NY EST",
     inputs: ["2021-03-14T05:15:59.000Z", "America/New_York"],
     result: "2021-03-14T00:15:59.000-0500",
   },
   {
-    desc: "UTC to 12:15am NY EST (2)",
+    desc: "ISO+Offset to 12:15am NY EST (2)",
     inputs: ["2021-03-14T00:15:59.000-0500", "America/New_York"],
     result: "2021-03-14T00:15:59.000-0500",
   },
   // 1:15am NY (non-DST)
   {
-    desc: "UTC to 1:15am NY EST",
+    desc: "UTC Zulu to 1:15am NY EST",
     inputs: ["2021-03-14T06:15:59.000Z", "America/New_York"],
     result: "2021-03-14T01:15:59.000-0500",
   },
   {
-    desc: "UTC to 1:15am NY EST (2)",
+    desc: "ISO+Offset to 1:15am NY EST (2)",
     inputs: ["2021-03-14T01:15:59.000-0500", "America/New_York"],
     result: "2021-03-14T01:15:59.000-0500",
   },
@@ -69,23 +72,23 @@ function testTzToUtc(t) {
 
   // 3:15am NY (DST)
   {
-    desc: "UTC to 3:15am NY EDT",
+    desc: "UTC Zulu to 3:15am NY EDT",
     inputs: ["2021-03-14T07:15:59.000Z", "America/New_York"],
     result: "2021-03-14T03:15:59.000-0400",
   },
   {
-    desc: "UTC to 3:15am NY EDT (2)",
+    desc: "ISO+Offset to 3:15am NY EDT (2)",
     inputs: ["2021-03-14T03:15:59.000-0400", "America/New_York"],
     result: "2021-03-14T03:15:59.000-0400",
   },
   // 4:15am NY
   {
-    desc: "UTC to 4:15am NY EDT",
+    desc: "UTC Zulu to 4:15am NY EDT",
     inputs: ["2021-03-14T08:15:59.000Z", "America/New_York"],
     result: "2021-03-14T04:15:59.000-0400",
   },
   {
-    desc: "UTC to 4:15am NY EDT (2)",
+    desc: "ISO+Offset to 4:15am NY EDT (2)",
     inputs: ["2021-03-14T04:15:59.000-0400", "America/New_York"],
     result: "2021-03-14T04:15:59.000-0400",
   },
@@ -106,57 +109,57 @@ function testTzToUtc(t) {
 
   // 12:15am NY -0400 => -0500
   {
-    desc: "UTC to 2021 Nov 7, 12:15am NY EDT",
+    desc: "UTC Zulu to 2021 Nov 7, 12:15am NY EDT",
     inputs: ["2021-11-07T04:15:59.000Z", "America/New_York"],
     result: "2021-11-07T00:15:59.000-0400",
   },
   {
-    desc: "UTC to 2021 Nov 7, 12:15am NY EDT (2)",
+    desc: "ISO+Offset to 2021 Nov 7, 12:15am NY EDT (2)",
     inputs: ["2021-11-07T00:15:59.000-0400", "America/New_York"],
     result: "2021-11-07T00:15:59.000-0400",
   },
   // 1:15am NY (DST) -0400
   // NOTE: 1:15am happens TWICE (with different offsets)
   {
-    desc: "UTC to 2021 Nov 7, 1:15am NY EDT",
+    desc: "UTC Zulu to 2021 Nov 7, 1:15am NY EDT",
     inputs: ["2021-11-07T05:15:59.000Z", "America/New_York"],
     result: "2021-11-07T01:15:59.000-0400",
   },
   {
-    desc: "UTC to 2021 Nov 7, 1:15am NY EDT (2)",
+    desc: "ISO+Offset to 2021 Nov 7, 1:15am NY EDT (2)",
     inputs: ["2021-11-07T01:15:59.000-0400", "America/New_York"],
     result: "2021-11-07T01:15:59.000-0400",
   },
   // 1:15am NY (non-DST) -0500
   {
-    desc: "UTC to 2021 Nov 7, 1:15am NY EST",
+    desc: "UTC Zulu to 2021 Nov 7, 1:15am NY EST",
     inputs: ["2021-11-07T06:15:59.000Z", "America/New_York"],
     result: "2021-11-07T01:15:59.000-0500",
   },
   {
-    desc: "UTC to 2021 Nov 7, 1:15am NY EST (2)",
+    desc: "ISO+Offset to 2021 Nov 7, 1:15am NY EST (2)",
     inputs: ["2021-11-07T01:15:59.000-0500", "America/New_York"],
     result: "2021-11-07T01:15:59.000-0500",
   },
   // 2:15am NY -0500
   {
-    desc: "UTC to 2021 Nov 7, 2:15am NY EST",
+    desc: "UTC Zulu to 2021 Nov 7, 2:15am NY EST",
     inputs: ["2021-11-07T07:15:59.000Z", "America/New_York"],
     result: "2021-11-07T02:15:59.000-0500",
   },
   {
-    desc: "UTC to 2021 Nov 7, 2:15am NY EST (2)",
+    desc: "ISO+Offset to 2021 Nov 7, 2:15am NY EST (2)",
     inputs: ["2021-11-07T02:15:59.000-0500", "America/New_York"],
     result: "2021-11-07T02:15:59.000-0500",
   },
   // 3:15am NY
   {
-    desc: "UTC to 2021 Nov 7, 3:15am NY EST",
+    desc: "UTC Zulu to 2021 Nov 7, 3:15am NY EST",
     inputs: ["2021-11-07T08:15:59.000Z", "America/New_York"],
     result: "2021-11-07T03:15:59.000-0500",
   },
   {
-    desc: "UTC to 2021 Nov 7, 3:15am NY EST (2)",
+    desc: "ISO+Offset to 2021 Nov 7, 3:15am NY EST (2)",
     inputs: ["2021-11-07T03:15:59.000-0500", "America/New_York"],
     result: "2021-11-07T03:15:59.000-0500",
   },
@@ -167,27 +170,29 @@ function testTzToUtc(t) {
 
   // Colombo +0530 (not DST)
   {
-    desc: "UTC to Asia/Colombo (1)",
+    desc: "UTC Zulu to Asia/Colombo (1)",
     inputs: ["2021-03-14T08:15:59.000Z", "Asia/Colombo"],
     result: "2021-03-14T13:45:59.000+0530",
   },
   {
-    desc: "UTC to Asia/Colombo (2)",
+    desc: "ISO+Offset to Asia/Colombo (2)",
     inputs: ["2021-03-14T13:45:59.000+0530", "Asia/Colombo"],
     result: "2021-03-14T13:45:59.000+0530",
   },
   {
-    desc: "UTC to Asia/Colombo (3)",
+    desc: "UTC Zulu to Asia/Colombo (3)",
     inputs: ["2021-11-07T08:15:59.000Z", "Asia/Colombo"],
     result: "2021-11-07T13:45:59.000+0530",
   },
   {
-    desc: "UTC to Asia/Colombo (4)",
+    desc: "ISO+Offset to Asia/Colombo (4)",
     inputs: ["2021-11-07T13:45:59.000+0530", "Asia/Colombo"],
     result: "2021-11-07T13:45:59.000+0530",
   },
 ].forEach(testUtcToTz);
-console.info("Pass: UTC to TZ for America/New_York and Asia/Colombo");
+console.info(
+  "Pass: UTC/ISO+Offset to TZ for America/New_York and Asia/Colombo"
+);
 
 [
   //
@@ -314,3 +319,16 @@ console.info("Pass: UTC to TZ for America/New_York and Asia/Colombo");
   },
 ].forEach(testTzToUtc);
 console.info("Pass: TZ to UTC for America/New_York and Asia/Colombo");
+
+var localISOString = TZ.toLocalISOString();
+var reISOString = /^\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d\.\d\d\d[+-]\d\d\d\d$/;
+if (!reISOString.test(localISOString)) {
+  throw new Error("Couldn't get local time as iso+offset");
+}
+console.info("Pass: can get local time as ISO+Offset");
+
+var tzName = TZ.timeZone();
+if (!/^[A-Z]\w+\/[A-Z]\w+$/.test(tzName)) {
+  throw new Error("Couldn't get local Time Zone");
+}
+console.info("Pass: can get local timezone");

xtz.js

@@ -103,7 +103,7 @@
   }
 
   function toOffsetISOString(date, timeZone) {
-    if ("offset" in date && "year" in date) {
+    if ("object" === typeof date && "offset" in date && "year" in date) {
       return formatAsOffsetISOString(date);
     }
 
@@ -179,6 +179,10 @@
     return `${YYYY}-${MM}-${DD}T${hh}:${mm}:${ss}.${sss}${offset}`;
   }
 
+  function getTimeZone() {
+    return new Intl.DateTimeFormat().resolvedOptions().timeZone;
+  }
+
   exports.XTZ = {
     // bespoke date =>
     // 2021-11-07T3:15:59-0500
@@ -190,6 +194,9 @@
     // -240 => -0400
     formatOffset: formatOffset,
 
+    // "America/New_York"
+    timeZone: getTimeZone,
+    // "2021-11-07T03:15:59-0500"
     toLocalISOString: toLocalISOString,
 
     // [ "2021-11-07T08:15:59Z", "America/New_York" ]