diff --git a/docs/GUIDE.md b/docs/GUIDE.md
index 0943a57cc..f5292bca5 100644
--- a/docs/GUIDE.md
+++ b/docs/GUIDE.md
@@ -294,7 +294,6 @@ IEnumerable<Quote> dayBarHistory =
 
 #### PeriodSize options (for newSize)
 
-- `PeriodSize.Month`
 - `PeriodSize.Week`
 - `PeriodSize.Day`
 - `PeriodSize.FourHours`
diff --git a/indicators/_Common/Functions.cs b/indicators/_Common/Functions.cs
index 097b9efbf..847040c8c 100644
--- a/indicators/_Common/Functions.cs
+++ b/indicators/_Common/Functions.cs
@@ -55,6 +55,7 @@ internal static TimeSpan ToTimeSpan(this PeriodSize periodSize)
                 PeriodSize.ThreeMinutes => TimeSpan.FromMinutes(3),
                 PeriodSize.FiveMinutes => TimeSpan.FromMinutes(5),
                 PeriodSize.FifteenMinutes => TimeSpan.FromMinutes(15),
+                PeriodSize.ThirtyMinutes => TimeSpan.FromMinutes(30),
                 PeriodSize.OneHour => TimeSpan.FromHours(1),
                 PeriodSize.TwoHours => TimeSpan.FromHours(2),
                 PeriodSize.FourHours => TimeSpan.FromHours(4),
diff --git a/tests/indicators/common/Test.Functions.cs b/tests/indicators/common/Test.Functions.cs
index 6e770a4a8..a855b9fc8 100644
--- a/tests/indicators/common/Test.Functions.cs
+++ b/tests/indicators/common/Test.Functions.cs
@@ -44,11 +44,13 @@ public void ToTimeSpan()
             Assert.AreEqual(PeriodSize.ThreeMinutes.ToTimeSpan(), TimeSpan.FromMinutes(3));
             Assert.AreEqual(PeriodSize.FiveMinutes.ToTimeSpan(), TimeSpan.FromMinutes(5));
             Assert.AreEqual(PeriodSize.FifteenMinutes.ToTimeSpan(), TimeSpan.FromHours(0.25));
+            Assert.AreEqual(PeriodSize.ThirtyMinutes.ToTimeSpan(), TimeSpan.FromHours(0.5));
             Assert.AreEqual(PeriodSize.OneHour.ToTimeSpan(), TimeSpan.FromMinutes(60));
             Assert.AreEqual(PeriodSize.TwoHours.ToTimeSpan(), TimeSpan.FromHours(2));
             Assert.AreEqual(PeriodSize.FourHours.ToTimeSpan(), TimeSpan.FromHours(4));
             Assert.AreEqual(PeriodSize.Day.ToTimeSpan(), TimeSpan.FromHours(24));
             Assert.AreEqual(PeriodSize.Week.ToTimeSpan(), TimeSpan.FromDays(7));
+
             Assert.AreEqual(PeriodSize.Month.ToTimeSpan(), TimeSpan.Zero);
         }
     }