suggested fixes + support for custom date format

bits/20_jsutils.js

@@ -130,8 +130,53 @@ function fuzzynum(s/*:string*/)/*:number*/ {
 	if(!isNaN(v = Number(ss))) return v / wt;
 	return v;
 }
-function fuzzydate(s/*:string*/)/*:Date*/ {
+
+// date regex reference - https://www.oreilly.com/library/view/regular-expressions-cookbook/9781449327453/ch04s04.html
+// matches mm/dd/yy, mm/dd/yyyy, dd/mm/yy, dd/mm/yyyy
+var STRICT_DATE_REGEX = [
+	"^(?:(1[0-2]|0[1-9])\\.(3[01]|[12][0-9]|0[1-9])|(3[01]|[12][0-9]|0[1-9])\\.(1[0-2]|0[1-9]))\\.([0-2][0-9]{3}|[0-9]{2})$", 
+	"^(?:(1[0-2]|0[1-9])\/(3[01]|[12][0-9]|0[1-9])|(3[01]|[12][0-9]|0[1-9])\/(1[0-2]|0[1-9]))\/([0-2][0-9]{3}|[0-9]{2})$",
+	"^(?:(1[0-2]|0[1-9])-(3[01]|[12][0-9]|0[1-9])|(3[01]|[12][0-9]|0[1-9])-(1[0-2]|0[1-9]))-([0-2][0-9]{3}|[0-9]{2})$",
+	"^(?:(1[0-2]|0[1-9])\\.(3[01]|[12][0-9]|0[1-9])|(3[01]|[12][0-9]|0[1-9])\\.(1[0-2]|0[1-9]))\\.([0-2][0-9]{3}|[0-9]{2})$",
+	"^(?:(1[0-2]|0[1-9])\/(3[01]|[12][0-9]|0[1-9])|(3[01]|[12][0-9]|0[1-9])\/(1[0-2]|0[1-9]))\/([0-2][0-9]{3}|[0-9]{2})$",
+	"^(?:(1[0-2]|0[1-9])-(3[01]|[12][0-9]|0[1-9])|(3[01]|[12][0-9]|0[1-9])-(1[0-2]|0[1-9]))-([0-2][0-9]{3}|[0-9]{2})$"
+	];
+
+function fuzzydate(s/*:string*/, strictDate/*string*/)/*:Date*/ {
 	var o = new Date(s), n = new Date(NaN);
+
+	if(strictDate) {
+		var dateFormat = strictDate.toLowerCase().replace(/[.]|[-]/g, '/')
+
+		STRICT_DATE_REGEX
+		.map(function (regex) {
+			var regexTestString = 
+			var matchStr = regexTestString.test(s)
+
+			if(matchStr){
+				s.replace(/[.]|[-]/g, '/')
+
+				if (dateFormat === "dd/mm") {
+					var splitDate = s.split('/')
+					var newDate = [s[1], s[0], s[2]]
+
+					s = newDate.join('/')
+
+					o = new Date(s)
+					return o
+				}
+				
+				o = new Date(s)
+				return o;
+			};
+	  	})
+		.filter(function (result) {
+			return ((result !== undefined) && (result !== null))
+		});
+
+		return n;
+	}
+
 	var y = o.getYear(), m = o.getMonth(), d = o.getDate();
 	if(isNaN(d)) return n;
 	if(y < 0 || y > 8099) return n;

bits/40_harb.js

@@ -883,7 +883,7 @@ var PRN = (function() {
 			else if(s == "TRUE") { cell.t = 'b'; cell.v = true; }
 			else if(s == "FALSE") { cell.t = 'b'; cell.v = false; }
 			else if(!isNaN(v = fuzzynum(s))) { cell.t = 'n'; if(o.cellText !== false) cell.w = s; cell.v = v; }
-			else if(!isNaN(fuzzydate(s).getDate()) || _re && s.match(_re)) {
+			else if(!isNaN(fuzzydate(s, o.strictDate).getDate()) || _re && s.match(_re)) {
 				cell.z = o.dateNF || SSF._table[14];
 				var k = 0;
 				if(_re && s.match(_re)){ s=dateNF_fix(s, o.dateNF, (s.match(_re)||[])); k=1; }