Fix issue #2037 - modifying a dayjs instance created with plugin timezone in UTC corrupts it

[BePo65]

Using 'UTC' (or any timezone with utcOffset 0) will return a false date.

This pr also fixes the following issues

• issue urgency-----Etc/GMT0 is Error #2108
• issue Modifying (.add(), .subtract(), etc.) a dayjs instance created in UTC corrupts it #2037
• issue Unexpected behavior with timezone "UTC" #2110
• issue After the local timezone is switched to Australia/Sydney, the output of the add method is wrong because winter time is not taken into account #2043
• issue .month() resets date property to 1 when in +00:00 UTC timezone #1860

To fix problems with date strings containing an offset, this solution has to differentiate between date strings with offset and one without that.
To differentiate a date only string (e.g. yy-mm-dd) from a date string with negative 2-digit offset (hour offset zz, e.g. yy-mm-zz) the changed code requires at least 8 characters before the offset (i.e. yy-mm-dd-zz).
This will not solve all possible format strings available by the CustomParseFormat, but should give no problems in real world applications.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (a947a51) 99.77% compared to head (4cb0ef7) 99.77%.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #2118   +/-   ##
=======================================
  Coverage   99.77%   99.77%           
=======================================
  Files         183      183           
  Lines        2262     2265    +3     
  Branches      641      641           
=======================================
+ Hits         2257     2260    +3     
  Misses          5        5           

Files Changed	Coverage Δ
src/plugin/utc/index.js	100.00% <ø> (ø)
src/plugin/timezone/index.js	100.00% <100.00%> (ø)

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[leemoria]

hello，I ask a question, When will the latest version be released ? @iamkun @BePo65

[michaelklassen02]

Hi, when is this PR going to be merged? I'm trying to convert a repository over to DayJS and we need UTC timezone support to work in order to use it.
@iamkun @BePo65

[Kestutis]

While waiting on PR to be merged, you can just get fixed timezone plugin and use it directly
get it from - https://github.com/BePo65/dayjs/blob/fix/issue2037/src/plugin/timezone/index.js
and then import yourself from your project and extend dayjs:

import timezoneDayjs from "./local/dayjs/plugin/timezone";
dayjs.extend(timezoneDayjs);

[nkeyy0]

Any updates related to this PR?

[litvinovvo]

Will it be merged any time soon? @iamkun

[zxd65885152]

hello, is there any updates with this PR?

[ateszki]

I think that with this changes it is safe to remove this previous change #1212

[Cheewbacca]

Any updates ?

[JugaruRobert]

Any updates about merging this? @iamkun

[jonah-ullman]

Hey there @iamkun, any updates on this? Thanks!

[andrashee]

What is blocking this PR to be merged @BePo65 @zomars? Having this fixed is crucial when working with tz and dayjs.

[BePo65]

waiting for @iamkun - I think this repository is dead. I am thinking about a fork that will merge all the important open pr.

[erikmellum]

@iamkun @BePo65 @zomars any update here?

[skoob13]

Patch for 1.11.11:

diff --git a/esm/plugin/timezone/index.js b/esm/plugin/timezone/index.js
index 490aff2e5cc5eb1186d03cfc9809242554928f99..5ffab621423cbea2d04242e674ce82e73f67c751 100644
--- a/esm/plugin/timezone/index.js
+++ b/esm/plugin/timezone/index.js
@@ -12,10 +12,6 @@ var typeToPos = {
 var dtfCache = {};
 
 var getDateTimeFormat = function getDateTimeFormat(timezone, options) {
-  if (options === void 0) {
-    options = {};
-  }
-
   var timeZoneName = options.timeZoneName || 'short';
   var key = timezone + "|" + timeZoneName;
   var dtf = dtfCache[key];
@@ -120,9 +116,13 @@ export default (function (o, c, d) {
       timeZone: timezone
     });
     var diff = Math.round((date - new Date(target)) / 1000 / 60);
-    var ins = d(target, {
-      locale: this.$L
-    }).$set(MS, this.$ms).utcOffset(-Math.round(date.getTimezoneOffset() / 15) * 15 - diff, true);
+    var offset = -date.getTimezoneOffset() - diff;
+
+    if (offset === 0) {
+      return this.utc(keepLocalTime);
+    }
+
+    var ins = d(target).$set(MS, this.$ms).utcOffset(offset, true);
 
     if (keepLocalTime) {
       var newOffset = ins.utcOffset();
@@ -161,11 +161,13 @@ export default (function (o, c, d) {
   d.tz = function (input, arg1, arg2) {
     var parseFormat = arg2 && arg1;
     var timezone = arg2 || arg1 || defaultTimezone;
-    var previousOffset = tzOffset(+d(), timezone);
+    var previousOffset = tzOffset(+d(input, parseFormat), timezone); // To differentiate date only string (e.g. yy-mm-dd) from date string with negative
+    // 2-digit offset (hour offset zz, e.g. yy-mm-zz) we require at least 8 characters
+    // before offset (i.e. yy-mm-dd-zz)
 
-    if (typeof input !== 'string') {
-      // timestamp number || js Date || Day.js
-      return d(input).tz(timezone);
+    if (typeof input !== 'string' || /.{8,}[+-]\d\d:?(\d\d)?$|Z$/i.test(input)) {
+      // timestamp number || js Date || Day.js || input string with offset (e.g. -03:00)
+      return d(input, parseFormat).tz(timezone);
     }
 
     var localTs = d.utc(input, parseFormat).valueOf();
diff --git a/plugin/timezone.js b/plugin/timezone.js
index b778bef4dd0e3b7690a96356343837a12ac8b58c..c465ba92379e2203bacdceb720abd542e882cf7a 100644
--- a/plugin/timezone.js
+++ b/plugin/timezone.js
@@ -1 +1 @@
-!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).dayjs_plugin_timezone=e()}(this,(function(){"use strict";var t={year:0,month:1,day:2,hour:3,minute:4,second:5},e={};return function(n,i,o){var r,a=function(t,n,i){void 0===i&&(i={});var o=new Date(t),r=function(t,n){void 0===n&&(n={});var i=n.timeZoneName||"short",o=t+"|"+i,r=e[o];return r||(r=new Intl.DateTimeFormat("en-US",{hour12:!1,timeZone:t,year:"numeric",month:"2-digit",day:"2-digit",hour:"2-digit",minute:"2-digit",second:"2-digit",timeZoneName:i}),e[o]=r),r}(n,i);return r.formatToParts(o)},u=function(e,n){for(var i=a(e,n),r=[],u=0;u<i.length;u+=1){var f=i[u],s=f.type,m=f.value,c=t[s];c>=0&&(r[c]=parseInt(m,10))}var d=r[3],l=24===d?0:d,h=r[0]+"-"+r[1]+"-"+r[2]+" "+l+":"+r[4]+":"+r[5]+":000",v=+e;return(o.utc(h).valueOf()-(v-=v%1e3))/6e4},f=i.prototype;f.tz=function(t,e){void 0===t&&(t=r);var n=this.utcOffset(),i=this.toDate(),a=i.toLocaleString("en-US",{timeZone:t}),u=Math.round((i-new Date(a))/1e3/60),f=o(a,{locale:this.$L}).$set("millisecond",this.$ms).utcOffset(15*-Math.round(i.getTimezoneOffset()/15)-u,!0);if(e){var s=f.utcOffset();f=f.add(n-s,"minute")}return f.$x.$timezone=t,f},f.offsetName=function(t){var e=this.$x.$timezone||o.tz.guess(),n=a(this.valueOf(),e,{timeZoneName:t}).find((function(t){return"timezonename"===t.type.toLowerCase()}));return n&&n.value};var s=f.startOf;f.startOf=function(t,e){if(!this.$x||!this.$x.$timezone)return s.call(this,t,e);var n=o(this.format("YYYY-MM-DD HH:mm:ss:SSS"),{locale:this.$L});return s.call(n,t,e).tz(this.$x.$timezone,!0)},o.tz=function(t,e,n){var i=n&&e,a=n||e||r,f=u(+o(),a);if("string"!=typeof t)return o(t).tz(a);var s=function(t,e,n){var i=t-60*e*1e3,o=u(i,n);if(e===o)return[i,e];var r=u(i-=60*(o-e)*1e3,n);return o===r?[i,o]:[t-60*Math.min(o,r)*1e3,Math.max(o,r)]}(o.utc(t,i).valueOf(),f,a),m=s[0],c=s[1],d=o(m).utcOffset(c);return d.$x.$timezone=a,d},o.tz.guess=function(){return Intl.DateTimeFormat().resolvedOptions().timeZone},o.tz.setDefault=function(t){r=t}}}));
\ No newline at end of file
+!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).dayjs_plugin_timezone=e()}(this,(function(){"use strict";var t={year:0,month:1,day:2,hour:3,minute:4,second:5},e={};return function(n,i,r){var o,a=function(t,n,i){void 0===i&&(i={});var r=new Date(t),o=function(t,n){var i=n.timeZoneName||"short",r=t+"|"+i,o=e[r];return o||(o=new Intl.DateTimeFormat("en-US",{hour12:!1,timeZone:t,year:"numeric",month:"2-digit",day:"2-digit",hour:"2-digit",minute:"2-digit",second:"2-digit",timeZoneName:i}),e[r]=o),o}(n,i);return o.formatToParts(r)},u=function(e,n){for(var i=a(e,n),o=[],u=0;u<i.length;u+=1){var f=i[u],s=f.type,m=f.value,c=t[s];c>=0&&(o[c]=parseInt(m,10))}var d=o[3],l=24===d?0:d,h=o[0]+"-"+o[1]+"-"+o[2]+" "+l+":"+o[4]+":"+o[5]+":000",v=+e;return(r.utc(h).valueOf()-(v-=v%1e3))/6e4},f=i.prototype;f.tz=function(t,e){void 0===t&&(t=o);var n=this.utcOffset(),i=this.toDate(),a=i.toLocaleString("en-US",{timeZone:t}),u=Math.round((i-new Date(a))/1e3/60),f=-i.getTimezoneOffset()-u;if(0===f)return this.utc(e);var s=r(a).$set("millisecond",this.$ms).utcOffset(f,!0);if(e){var m=s.utcOffset();s=s.add(n-m,"minute")}return s.$x.$timezone=t,s},f.offsetName=function(t){var e=this.$x.$timezone||r.tz.guess(),n=a(this.valueOf(),e,{timeZoneName:t}).find((function(t){return"timezonename"===t.type.toLowerCase()}));return n&&n.value};var s=f.startOf;f.startOf=function(t,e){if(!this.$x||!this.$x.$timezone)return s.call(this,t,e);var n=r(this.format("YYYY-MM-DD HH:mm:ss:SSS"),{locale:this.$L});return s.call(n,t,e).tz(this.$x.$timezone,!0)},r.tz=function(t,e,n){var i=n&&e,a=n||e||o,f=u(+r(t,i),a);if("string"!=typeof t||/.{8,}[+-]\d\d:?(\d\d)?$|Z$/i.test(t))return r(t,i).tz(a);var s=function(t,e,n){var i=t-60*e*1e3,r=u(i,n);if(e===r)return[i,e];var o=u(i-=60*(r-e)*1e3,n);return r===o?[i,r]:[t-60*Math.min(r,o)*1e3,Math.max(r,o)]}(r.utc(t,i).valueOf(),f,a),m=s[0],c=s[1],d=r(m).utcOffset(c);return d.$x.$timezone=a,d},r.tz.guess=function(){return Intl.DateTimeFormat().resolvedOptions().timeZone},r.tz.setDefault=function(t){o=t}}}));