Add ability to now macro to return same UTC string used in date fields (#2884)

* Add ability to now macro to return same UTC string used in the modified and created fields.

* Revert "Add ability to now macro to return same UTC string used in the modified and created fields."

This reverts commit 7b6ad7db4ae3058d5cf0d8858cdb24d44224ef69.

* Mods to formatDateString to adjust displayed date to UTC for [UTC]
format. Corresponding doc changes, and optimization for special
case.

core/modules/utils/utils.js

@@ -267,6 +267,9 @@ exports.formatDateString = function(date,template) {
 			[/^0ss/, function() {
 				return $tw.utils.pad(date.getSeconds());
 			}],
+			[/^0XXX/, function() {
+				return $tw.utils.pad(date.getMilliseconds());
+			}],
 			[/^0DD/, function() {
 				return $tw.utils.pad(date.getDate());
 			}],
@@ -308,6 +311,9 @@ exports.formatDateString = function(date,template) {
 			[/^ss/, function() {
 				return date.getSeconds();
 			}],
+			[/^XXX/, function() {
+				return date.getMilliseconds();
+			}],
 			[/^[AP]M/, function() {
 				return $tw.utils.getAmPm(date).toUpperCase();
 			}],
@@ -324,6 +330,16 @@ exports.formatDateString = function(date,template) {
 				return $tw.utils.pad(date.getFullYear() - 2000);
 			}]
 		];
+	// If the user wants everything in UTC, shift the datestamp
+	// Optimize for format string that essentially means 
+	// 'return raw UTC (tiddlywiki style) date string.'
+	if(t.indexOf("[UTC]") == 0 ) {
+		if(t == "[UTC]YYYY0MM0DD0hh0mm0ssXXX") 
+			return $tw.utils.stringifyDate(new Date());
+		var offset = date.getTimezoneOffset() ; // in minutes
+		date = new Date(date.getTime()+offset*60*1000) ;
+		t = t.substr(5) ;
+	} 
 	while(t.length){
 		var matchString = "";
 		$tw.utils.each(matches, function(m) {

editions/tw5.com/tiddlers/features/DateFormat.tid

@@ -1,5 +1,5 @@
 created: 20140418142957325
-modified: 20140912145809035
+modified: 20170630223008226
 tags: Features
 title: DateFormat
 type: text/vnd.tiddlywiki
@@ -30,10 +30,13 @@ The ViewWidget accepts a `template` attribute that allows the format of date val
 |`0mm` |Minutes with leading zero |
 |`ss` |Seconds |
 |`0ss` |Seconds with leading zero |
+|`XXX` |Milliseconds |
+|`0XXX` |Milliseconds with leading zero |
 |`am` or `pm` |Lower case AM/PM indicator |
 |`AM` or `PM` |Upper case AM/PM indicator |
 |`TZD` |Timezone offset |
 |`\x` |Used to escape a character that would otherwise have special meaning |
+|`[UTC]`|Time-shift the represented date to UTC. Must be at very start of format string|
 
 Note that other text is passed through unchanged, allowing commas, colons or other separators to be used.
 

editions/tw5.com/tiddlers/macros/NowMacro.tid

@@ -1,6 +1,6 @@
 caption: now
 created: 20141008141616791
-modified: 20150221170300000
+modified: 20170630223406157
 tags: Macros [[Core Macros]]
 title: now Macro
 type: text/vnd.tiddlywiki
@@ -14,4 +14,7 @@ The value doesn't update automatically, like a ticking clock. It updates wheneve
 ;format
 : A string specifying the desired [[format|DateFormat]], defaulting to `0hh:0mm, DDth MMM YYYY`
 
+''Note'': The format string `[UTC]YYYY0MM0DD0hh0mm0ssXXX` will return a date string representing the UTC time-stamp as it is used in the ~TiddlyWiki `created` and `modified` time-stamp fields.
+
+
 <<.macro-examples "now">>