diff --git a/src/Skybrud.Essentials/Time/EssentialsDate.cs b/src/Skybrud.Essentials/Time/EssentialsDate.cs
index d227163..222ed4f 100644
--- a/src/Skybrud.Essentials/Time/EssentialsDate.cs
+++ b/src/Skybrud.Essentials/Time/EssentialsDate.cs
@@ -439,7 +439,7 @@ public string ToString([StringSyntax(StringSyntaxAttribute.DateTimeFormat)] stri
         /// <param name="provider">An object that supplies culture-specific formatting information.</param>
         /// <returns>A string representation of value of the current <see cref="EssentialsDate"/> object as specified by <paramref name="format"/> and <paramref name="provider"/>.</returns>
         public string ToString([StringSyntax(StringSyntaxAttribute.DateTimeFormat)] string? format, IFormatProvider? provider) {
-            return _dateTime.ToString(format, provider);
+            return _dateTime.ToString(string.IsNullOrWhiteSpace(format) ? "yyyy-MM-dd" : format, provider);
         }
 
         #endregion
diff --git a/src/Skybrud.Essentials/Time/EssentialsTime.cs b/src/Skybrud.Essentials/Time/EssentialsTime.cs
index 802d144..ff0a18c 100644
--- a/src/Skybrud.Essentials/Time/EssentialsTime.cs
+++ b/src/Skybrud.Essentials/Time/EssentialsTime.cs
@@ -791,7 +791,7 @@ public string ToString([StringSyntax(StringSyntaxAttribute.DateTimeFormat)] stri
         /// <param name="provider">An object that supplies culture-specific formatting information.</param>
         /// <returns>A string representation of value of the current <see cref="EssentialsTime"/> object as specified by <paramref name="format"/> and <paramref name="provider"/>.</returns>
         public string ToString([StringSyntax(StringSyntaxAttribute.DateTimeFormat)] string? format, IFormatProvider? provider) {
-            return DateTimeOffset.ToString(format, provider);
+            return string.IsNullOrWhiteSpace(format) ? Iso8601 : DateTimeOffset.ToString(format, provider);
         }
 
         /// <summary>
diff --git a/src/TestProject1/Time/EssentialsDateTests.cs b/src/TestProject1/Time/EssentialsDateTests.cs
index 532066d..18e6ac8 100644
--- a/src/TestProject1/Time/EssentialsDateTests.cs
+++ b/src/TestProject1/Time/EssentialsDateTests.cs
@@ -13,8 +13,9 @@ public void ToStringDefault() {
 
         EssentialsDate date = new(2024, 3, 27);
 
-        Assert.AreEqual("2024-03-27", date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture));
-        Assert.AreEqual("2024-03-27", date.ToString("yyyy-MM-dd", CultureInfo.GetCultureInfo("da-DK")));
+        Assert.AreEqual("2024-03-27", date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture), "#1");
+        Assert.AreEqual("2024-03-27", date.ToString("yyyy-MM-dd", CultureInfo.GetCultureInfo("da-DK")), "#2");
+        Assert.AreEqual("2024-03-27", $"{date}", "#3");
 
     }
 
diff --git a/src/TestProject1/Time/EssentialsTimeTests.cs b/src/TestProject1/Time/EssentialsTimeTests.cs
index 9a54ec2..1053887 100644
--- a/src/TestProject1/Time/EssentialsTimeTests.cs
+++ b/src/TestProject1/Time/EssentialsTimeTests.cs
@@ -13,7 +13,8 @@ public void ToStringDefault() {
 
         EssentialsTime time = new(2024, 3, 27, 12, 0, 0, TimeZoneInfo.Utc);
 
-        Assert.AreEqual("2024-03-27T12:00:00.000Z", time.ToString());
+        Assert.AreEqual("2024-03-27T12:00:00.000Z", time.ToString(), "#1");
+        Assert.AreEqual("2024-03-27T12:00:00.000Z", $"{time}", "#2");
 
     }
 
diff --git a/src/UnitTestProject1/Time/Time/EssentialsDateTests.cs b/src/UnitTestProject1/Time/Time/EssentialsDateTests.cs
index 23db8f2..55543de 100644
--- a/src/UnitTestProject1/Time/Time/EssentialsDateTests.cs
+++ b/src/UnitTestProject1/Time/Time/EssentialsDateTests.cs
@@ -235,6 +235,17 @@ public void Max() {
 
         }
 
+        [TestMethod]
+        public void ToStringDefault() {
+
+            EssentialsDate date = new EssentialsDate(2024, 4, 7);
+
+            Assert.AreEqual("2024-04-07", date.ToString());
+            Assert.AreEqual("2024-04-07", $"{date}");
+            Assert.AreEqual("2024-04-07", $"{date:yyyy-MM-dd}");
+
+        }
+
     }
 
 }
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