diff --git a/README.md b/README.md
index 451ba36..85d60e1 100644
--- a/README.md
+++ b/README.md
@@ -13,10 +13,11 @@ Usage:
   Rotationator <lastByaml> <outputByaml> [options]
 
 Arguments:
-  <lastByaml>  The last VSSetting BYAML file.
+  <lastByaml>    The last VSSetting BYAML file.
   <outputByaml>  The output VSSetting BYAML file.
 
 Options:
-  --version       Show version information
-  -?, -h, --help  Show help and usage information
+  --phaseLength <phaseLength>  The length of each phase, in hours. [default: 4]
+  --version                    Show version information
+  -?, -h, --help               Show help and usage information
 ```
diff --git a/Rotationator/Program.cs b/Rotationator/Program.cs
index 9ddf206..dd09435 100644
--- a/Rotationator/Program.cs
+++ b/Rotationator/Program.cs
@@ -1,4 +1,4 @@
-using System.CommandLine;
+using System.CommandLine;
 using System.CommandLine.Invocation;
 using System.Text.Json;
 using OatmealDome.BinaryData;
@@ -11,6 +11,7 @@ using Rotationator;
 //
 
 const int maximumPhases = 192; // TODO correct?
+const int defaultPhaseLength = 4;
 
 Dictionary<VersusRule, List<int>> bannedStages = new Dictionary<VersusRule, List<int>>()
 {
@@ -63,10 +64,14 @@ Argument<string> lastByamlArg = new Argument<string>("lastByaml", "The last VSSe
 
 Argument<string> outputByamlArg = new Argument<string>("outputByaml", "The output VSSetting BYAML file.");
 
+Option<int> phaseLengthOption =
+    new Option<int>("--phaseLength", () => defaultPhaseLength, "The length of each phase in hours.");
+
 Command command = new RootCommand("Generates a new VSSetting BYAMl file.")
 {
     lastByamlArg,
-    outputByamlArg
+    outputByamlArg,
+    phaseLengthOption
 };
 
 command.SetHandler(context => Run(context));
@@ -83,6 +88,7 @@ void Run(InvocationContext context)
 
     string lastByamlPath = context.ParseResult.GetValueForArgument(lastByamlArg);
     string outputByamlPath = context.ParseResult.GetValueForArgument(outputByamlArg);
+    int phaseLength = context.ParseResult.GetValueForOption(phaseLengthOption);
     
     dynamic lastByaml = ByamlFile.Load(lastByamlPath);
     
@@ -127,7 +133,7 @@ void Run(InvocationContext context)
     }
 
     // The last phase is set to 10 years, so correct this to the correct phase length.
-    currentPhases.Last().Length = 4;
+    currentPhases.Last().Length = phaseLength;
     
     //
     // Generate new phases to fill out the schedule
@@ -161,7 +167,7 @@ void Run(InvocationContext context)
         currentPhase.GachiInfo.Stages.Add(PickStage(currentPhase, lastPhase, gachiRule, stagePools[gachiRule]));
         currentPhase.GachiInfo.Stages.Sort();
         
-        currentPhase.Length = 4;
+        currentPhase.Length = phaseLength;
         
         currentPhases.Add(currentPhase);
     }
@@ -274,4 +280,4 @@ int PickStage(GambitVersusPhase phase, GambitVersusPhase lastPhase, VersusRule r
     }
 
     return GetRandomElementFromPool(pool, IsStageValid);
-}
\ No newline at end of file
+}