diff --git a/include/lbt/populations/indexing/indexing.hpp b/include/lbt/populations/indexing/indexing.hpp
index 4d4914d..12ee9e6 100755
--- a/include/lbt/populations/indexing/indexing.hpp
+++ b/include/lbt/populations/indexing/indexing.hpp
@@ -13,40 +13,11 @@
 #include <tuple>
 
 #include "lbt/common/type_definitions.hpp"
+#include "lbt/populations/indexing/timestep.hpp"
 
 
 namespace lbt {
 
-  /**\enum  Timestep
-   * \brief Strongly typed enum for even and odd time steps required for AA access pattern
-   */
-  enum class Timestep: bool {
-    Even = false,
-    Odd = true
-  };
-
-  /**\fn        operator!
-   * \brief     Negation operator for the timestep
-   *
-   * \param[in] ts   Timestep to be negated
-   * \return    Negated timestep
-   */
-  inline constexpr Timestep operator! (Timestep const& ts) noexcept {
-    return (ts == Timestep::Even) ? Timestep::Odd : Timestep::Even;
-  }
-
-  /**\fn            Timestep output stream operator
-   * \brief         Output stream operator for the timestep
-   *
-   * \param[in,out] os   Output stream
-   * \param[in]     ts   Timestep to be printed to output stream
-   * \return        Output stream including the type of timestep
-   */
-  inline std::ostream& operator << (std::ostream& os, Timestep const& ts) noexcept {
-    os << ((ts == Timestep::Even) ? "even time step" : "odd time step");
-    return os;
-  }
-
   /**\class  Indexing
    * \brief  Class for indexing of a population
    *
diff --git a/include/lbt/populations/indexing/timestep.hpp b/include/lbt/populations/indexing/timestep.hpp
new file mode 100755
index 0000000..090819b
--- /dev/null
+++ b/include/lbt/populations/indexing/timestep.hpp
@@ -0,0 +1,48 @@
+/**
+ * \file     timestep.hpp
+ * \brief    Base class for timestep
+ * \author   Tobit Flatscher (github.com/2b-t)
+*/
+
+#ifndef LBT__INDEXING__TIMESTEP
+#define LBT__INDEXING__TIMESTEP
+#pragma once
+
+#include <ostream>
+
+
+namespace lbt {
+
+  /**\enum  Timestep
+   * \brief Strongly typed enum for even and odd time steps required for AA access pattern
+   */
+  enum class Timestep: bool {
+    Even = false,
+    Odd = true
+  };
+
+  /**\fn        operator!
+   * \brief     Negation operator for the timestep
+   *
+   * \param[in] ts   Timestep to be negated
+   * \return    Negated timestep
+   */
+  inline constexpr Timestep operator! (Timestep const& ts) noexcept {
+    return (ts == Timestep::Even) ? Timestep::Odd : Timestep::Even;
+  }
+
+  /**\fn            Timestep output stream operator
+   * \brief         Output stream operator for the timestep
+   *
+   * \param[in,out] os   Output stream
+   * \param[in]     ts   Timestep to be printed to output stream
+   * \return        Output stream including the type of timestep
+   */
+  inline std::ostream& operator << (std::ostream& os, Timestep const& ts) noexcept {
+    os << ((ts == Timestep::Even) ? "even time step" : "odd time step");
+    return os;
+  }
+
+}
+
+#endif // LBT__INDEXING__TIMESTEP