diff --git a/CHANGELOG.md b/CHANGELOG.md
index c1b0057e..004cfadf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Updated tzdata to fix issues with 2024b
 - Fix deprecation: Module.eval_quoted/4 is deprecated. Use Code.eval_quoted/3 instead
 - Fix deprecation: "min..max inside match is deprecated"
+- Fix deprecation: default arguments in protocol definitions are deprecated in Elixir 1.20 (`Timex.Comparable.compare/3`, `Timex.Comparable.diff/3`, `Timex.Protocol.to_datetime/2`)
 
 ---
 
diff --git a/lib/comparable/comparable.ex b/lib/comparable/comparable.ex
index 307ca271..82ba2627 100644
--- a/lib/comparable/comparable.ex
+++ b/lib/comparable/comparable.ex
@@ -81,7 +81,7 @@ defprotocol Timex.Comparable do
       0
   """
   @spec compare(comparable, comparable, granularity) :: compare_result
-  def compare(a, b, granularity \\ :microsecond)
+  def compare(a, b, granularity)
 
   @doc """
   Get the difference between two date or datetime types.
@@ -136,5 +136,5 @@ defprotocol Timex.Comparable do
       0
   """
   @spec diff(comparable, comparable, granularity) :: diff_result
-  def diff(a, b, granularity \\ :microsecond)
+  def diff(a, b, granularity)
 end
diff --git a/lib/protocol.ex b/lib/protocol.ex
index 6d387309..1a6249ac 100644
--- a/lib/protocol.ex
+++ b/lib/protocol.ex
@@ -42,10 +42,9 @@ defprotocol Timex.Protocol do
   Convert a date/time value to a DateTime.
   An optional timezone can be provided, UTC will be assumed if one is not provided.
   """
-  @spec to_datetime(Types.valid_datetime()) :: DateTime.t() | {:error, term}
   @spec to_datetime(Types.valid_datetime(), Types.valid_timezone()) ::
           DateTime.t() | Timex.AmbiguousDateTime.t() | {:error, term}
-  def to_datetime(datetime, timezone \\ :utc)
+  def to_datetime(datetime, timezone)
 
   @doc """
   Convert a date/time value to a NaiveDateTime
diff --git a/lib/timex.ex b/lib/timex.ex
index 8c7c8ea9..b21ac815 100644
--- a/lib/timex.ex
+++ b/lib/timex.ex
@@ -1021,7 +1021,7 @@ defmodule Timex do
     compare(a, b, :microseconds)
   end
 
-  defdelegate compare(a, b), to: Timex.Comparable
+  def compare(a, b), do: Timex.Comparable.compare(a, b, :microsecond)
 
   @doc """
   Compare two `Timex.Comparable` values, returning one of the following values:
@@ -1090,7 +1090,7 @@ defmodule Timex do
   @spec diff(Time.t() | Comparable.comparable(), Time.t() | Comparable.comparable()) ::
           Duration.t() | integer | {:error, term}
   def diff(%Time{} = a, %Time{} = b), do: diff(a, b, :microseconds)
-  defdelegate diff(a, b), to: Timex.Comparable
+  def diff(a, b), do: Timex.Comparable.diff(a, b, :microsecond)
 
   @doc """
   Calculate time interval between two dates. The result will be a signed integer, negative