diff --git a/js/Tiddler.js b/js/Tiddler.js
index 24efb55a7..0c1ad5786 100755
--- a/js/Tiddler.js
+++ b/js/Tiddler.js
@@ -8,29 +8,82 @@ and 'created' fields are dates. All other fields are strings.
 
 The Tiddler object exposes the following API
 
-new Tiddler(fields) - create a Tiddler given a hashmap of field values
-new Tiddler(tiddler,fields) - create a Tiddler from an existing tiddler with a hashmap of modified field values
+new Tiddler(src) - create a Tiddler given a hashmap of field values or a tiddler to clone
+new Tiddler(src1,src2) - create a Tiddler with the union of the fields from the
+						sources, with the rightmost taking priority
 Tiddler.fields - hashmap of tiddler fields
 
+The hashmap(s) can specify the  "modified" and "created" fields as strings in YYYYMMDDHHMMSSMMM
+format or as JavaScript date objects. The "tags" field can be given as a JavaScript array of strings or
+as a TiddlyWiki quoted string (eg, "one [[two three]]").
+
 */
 
 "use strict";
 
 var Tiddler = function(/* tiddler,fields */) {
-	var tiddler, fields, c = 0, t;
-	if(arguments[c] instanceof Tiddler) {
-		tiddler = arguments[c++];
-	}
-	fields = arguments[c++];
 	this.fields = {};
-	if(tiddler instanceof Tiddler) {
-		for(t in tiddler.fields) {
-			this.fields[t] = tiddler.fields[t]; // Should copy arrays by value
+	for(var c=0; c<arguments.length; c++) {
+		var arg = arguments[c],
+			src = null;
+		if(arg instanceof Tiddler) {
+			src = arg.fields;
+		} else {
+			src = arg;
+		}
+		for(var t in src) {
+			var f = this.parseField(t,src[t]);
+			if(f !== null) {
+				this.fields[t] = f;
+			}
 		}
 	}
-	for(t in fields) {
-		this.fields[t] = fields[t]; // Should copy arrays by value
+};
+
+Tiddler.prototype.parseField = function(name,value) {
+	var type = Tiddler.specialFields[name];
+	if(type) {
+		return Tiddler.specialParsers[type](value);
+	} else if (typeof value === "string") {
+		return value;
+	} else {
+		return null;
 	}
-}
+};
+
+// These are the non-string fields
+Tiddler.specialFields = {
+	"created": "date",
+	"modified": "date",
+	"tags": "array"
+};
+
+Tiddler.specialParsers = {
+	date: function(value) {
+		if(typeof value === "string") {
+			return utils.convertFromYYYYMMDDHHMMSSMMM(value);
+		} else if (value instanceof Date) {
+			return value;
+		} else {
+			return null;
+		}
+	},
+	array: function(value) {
+		if(typeof value === "string") {
+			var parser = new ArgParser(value,{noNames: true});
+			return parser.getValuesByName("","");
+		} else if (value instanceof Array) {
+			var result = [];
+			for(var t=0; t<value.length; t++) {
+				if(typeof value[t] === "string") {
+					result.push(value[t]);
+				}
+			}
+			return result;
+		} else {
+			return null;
+		}
+	}
+};
 
 exports.Tiddler = Tiddler;