add DAYS formula

cell/model/FormulaObjects/dateandtimeFunctions.js

@@ -289,7 +289,7 @@
 	}
 
 	cFormulaFunctionGroup['DateAndTime'] = cFormulaFunctionGroup['DateAndTime'] || [];
-	cFormulaFunctionGroup['DateAndTime'].push(cDATE, cDATEDIF, cDATEVALUE, cDAY, cDAYS360, cEDATE, cEOMONTH, cHOUR,
+	cFormulaFunctionGroup['DateAndTime'].push(cDATE, cDATEDIF, cDATEVALUE, cDAY, cDAYS, cDAYS360, cEDATE, cEOMONTH, cHOUR,
 		cMINUTE, cMONTH, cNETWORKDAYS, cNETWORKDAYS_INTL, cNOW, cSECOND, cTIME, cTIMEVALUE, cTODAY, cWEEKDAY, cWEEKNUM,
 		cWORKDAY, cWORKDAY_INTL, cYEAR, cYEARFRAC);
 
@@ -586,6 +586,94 @@
 		}
 	};
 
+	/**
+	 * @constructor
+	 * @extends {AscCommonExcel.cBaseFunction}
+	 */
+	function cDAYS() {
+		this.name = "DAYS";
+		this.value = null;
+		this.argumentsCurrent = 0;
+	}
+
+	cDAYS.prototype = Object.create(cBaseFunction.prototype);
+	cDAYS.prototype.constructor = cDAYS;
+	cDAYS.prototype.argumentsMin = 2;
+	cDAYS.prototype.argumentsMax = 2;
+	cDAYS.prototype.numFormat = AscCommonExcel.cNumFormatNone;
+	cDAYS.prototype.Calculate = function (arg) {
+		var arg0 = arg[0], val, arg1 = arg[1], val1;
+		if (arg0 instanceof cArray) {
+			arg0 = arg0.getElement(0);
+		} else if (arg0 instanceof cArea || arg0 instanceof cArea3D) {
+			arg0 = arg0.cross(arguments[1]).tocNumber();
+			val = arg0.tocNumber().getValue();
+		}
+		if (arg0 instanceof cError) {
+			return this.value = arg0;
+		} else if (arg0 instanceof cNumber || arg0 instanceof cBool) {
+			val = arg0.tocNumber().getValue();
+		} else if (arg0 instanceof cRef || arg0 instanceof cRef3D) {
+			val = arg0.getValue().tocNumber();
+			if (val instanceof cNumber || val instanceof cBool) {
+				val = arg0.tocNumber().getValue();
+			} else {
+				return this.value = new cError(cErrorType.wrong_value_type);
+			}
+		} else if (arg0 instanceof cString) {
+			val = arg0.tocNumber();
+			if (val instanceof cError || val instanceof cEmpty) {
+				var d = new Date(arg0.getValue());
+				if (isNaN(d)) {
+					return this.value = new cError(cErrorType.wrong_value_type);
+				} else {
+					val = Math.floor(( d.getTime() / 1000 - d.getTimezoneOffset() * 60 ) / c_sPerDay +
+						( AscCommonExcel.c_DateCorrectConst + (AscCommon.bDate1904 ? 0 : 1) ));
+				}
+			} else {
+				val = arg0.tocNumber().getValue();
+			}
+		}
+
+		if (arg1 instanceof cArray) {
+			arg1 = arg1.getElement(0);
+		} else if (arg1 instanceof cArea || arg1 instanceof cArea3D) {
+			arg1 = arg1.cross(arguments[1]).tocNumber();
+			val1 = arg1.tocNumber().getValue();
+		}
+		if (arg1 instanceof cError) {
+			return this.value = arg1;
+		} else if (arg1 instanceof cNumber || arg1 instanceof cBool) {
+			val1 = arg1.tocNumber().getValue();
+		} else if (arg1 instanceof cRef || arg1 instanceof cRef3D) {
+			val1 = arg1.getValue().tocNumber();
+			if (val1 instanceof cNumber || val1 instanceof cBool) {
+				val1 = arg1.tocNumber().getValue();
+			} else {
+				return this.value = new cError(cErrorType.wrong_value_type);
+			}
+		} else if (arg1 instanceof cString) {
+			val1 = arg1.tocNumber();
+			if (val1 instanceof cError || val1 instanceof cEmpty) {
+				var d = new Date(arg1.getValue());
+				if (isNaN(d)) {
+					return this.value = new cError(cErrorType.wrong_value_type);
+				} else {
+					val1 = Math.floor(( d.getTime() / 1000 - d.getTimezoneOffset() * 60 ) / c_sPerDay +
+						( AscCommonExcel.c_DateCorrectConst + (AscCommon.bDate1904 ? 0 : 1) ));
+				}
+			} else {
+				val1 = arg1.tocNumber().getValue();
+			}
+		}
+
+		if (val < 0 || val1 < 0) {
+			return this.value = new cError(cErrorType.not_numeric);
+		}else{
+			return this.value = new cNumber(val1 - val);
+		}
+	};
+
 	/**
 	 * @constructor
 	 * @extends {AscCommonExcel.cBaseFunction}