diff --git a/ClosedXML/Excel/CalcEngine/Expression.cs b/ClosedXML/Excel/CalcEngine/Expression.cs
index 6f078c2..f309af7 100644
--- a/ClosedXML/Excel/CalcEngine/Expression.cs
+++ b/ClosedXML/Excel/CalcEngine/Expression.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Text;
+using System.Threading;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -25,7 +26,6 @@
 		#region ** fields
 
 		internal Token _token;
-		static CultureInfo _ci = CultureInfo.InvariantCulture;
 
 		#endregion
 
@@ -103,6 +103,7 @@
 			}
 
 			// handle everything else
+			CultureInfo _ci = Thread.CurrentThread.CurrentCulture;
 			return (double)Convert.ChangeType(v, typeof(double), _ci);
 		}
 		public static implicit operator bool(Expression x)
@@ -149,6 +150,7 @@
 			}
 
 			// handle everything else
+			CultureInfo _ci = Thread.CurrentThread.CurrentCulture;
 			return (DateTime)Convert.ChangeType(v, typeof(DateTime), _ci);
 		}
 
@@ -490,7 +492,7 @@
 		}
 		public IEnumerator GetEnumerator()
 		{
-		    return (_value as IEnumerable).GetEnumerator();
+			return (_value as IEnumerable).GetEnumerator();
 		}
 	}
 	/// <summary>
diff --git a/ClosedXML_Tests/Excel/CalcEngine/DateAndTimeTests.cs b/ClosedXML_Tests/Excel/CalcEngine/DateAndTimeTests.cs
index a5c20dc..6213f8c 100644
--- a/ClosedXML_Tests/Excel/CalcEngine/DateAndTimeTests.cs
+++ b/ClosedXML_Tests/Excel/CalcEngine/DateAndTimeTests.cs
@@ -1,4 +1,6 @@
 using System;
+using System.Globalization;
+using System.Threading;
 using ClosedXML.Excel;
 using NUnit.Framework;
 
@@ -10,6 +12,12 @@
     [TestFixture]
     public class DateAndTimeTests
     {
+        [OneTimeSetUp]
+        public void SetCultureInfo()
+        {
+            Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-US");
+        }
+
         [Test]
         public void Date()
         {
@@ -32,6 +40,16 @@
         }
 
         [Test]
+        public void DayWithDifferentCulture()
+        {
+            CultureInfo ci = new CultureInfo(CultureInfo.InvariantCulture.LCID);
+            ci.DateTimeFormat.ShortDatePattern = "dd/MM/yyyy";
+            Thread.CurrentThread.CurrentCulture = ci;
+            Object actual = XLWorkbook.EvaluateExpr("Day(\"1/6/2008\")");
+            Assert.AreEqual(1, actual);
+        }
+
+        [Test]
         public void Days360_Default()
         {
             Object actual = XLWorkbook.EvaluateExpr("Days360(\"1/30/2008\", \"2/1/2008\")");