diff --git a/CMakeLists.txt b/CMakeLists.txt
index fd30d7ea..bd1e0be0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -150,8 +150,7 @@ endfunction()
 
 # Define the fmt library, its includes and the needed defines.
 add_headers(FMT_HEADERS chrono.h color.h compile.h core.h format.h format-inl.h
-                        locale.h ostream.h posix.h printf.h ranges.h
-                        safe-duration-cast.h)
+                        locale.h ostream.h posix.h printf.h ranges.h)
 set(FMT_SOURCES src/format.cc src/posix.cc)
 
 add_library(fmt ${FMT_SOURCES} ${FMT_HEADERS} README.rst ChangeLog.rst)
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index c88933b2..9abe7c4f 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -16,16 +16,291 @@
 #include <locale>
 #include <sstream>
 
-// enable safe chrono durations, unless explicitly disabled
+FMT_BEGIN_NAMESPACE
+
+// Enable safe chrono durations, unless explicitly disabled.
 #ifndef FMT_SAFE_DURATION_CAST
 #  define FMT_SAFE_DURATION_CAST 1
 #endif
-
 #if FMT_SAFE_DURATION_CAST
-#  include "safe-duration-cast.h"
-#endif
 
-FMT_BEGIN_NAMESPACE
+// For conversion between std::chrono::durations without undefined
+// behaviour or erroneous results.
+// This is a stripped down version of duration_cast, for inclusion in fmt.
+// See https://github.com/pauldreik/safe_duration_cast
+//
+// Copyright Paul Dreik 2019
+namespace safe_duration_cast {
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
+                        std::numeric_limits<From>::is_signed ==
+                            std::numeric_limits<To>::is_signed)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  using F = std::numeric_limits<From>;
+  using T = std::numeric_limits<To>;
+  static_assert(F::is_integer, "From must be integral");
+  static_assert(T::is_integer, "To must be integral");
+
+  // A and B are both signed, or both unsigned.
+  if (F::digits <= T::digits) {
+    // From fits in To without any problem.
+  } else {
+    // From does not always fit in To, resort to a dynamic check.
+    if (from < T::min() || from > T::max()) {
+      // outside range.
+      ec = 1;
+      return {};
+    }
+  }
+  return static_cast<To>(from);
+}
+
+/**
+ * converts From to To, without loss. If the dynamic value of from
+ * can't be converted to To without loss, ec is set.
+ */
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
+                        std::numeric_limits<From>::is_signed !=
+                            std::numeric_limits<To>::is_signed)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  using F = std::numeric_limits<From>;
+  using T = std::numeric_limits<To>;
+  static_assert(F::is_integer, "From must be integral");
+  static_assert(T::is_integer, "To must be integral");
+
+  if (F::is_signed && !T::is_signed) {
+    // From may be negative, not allowed!
+    if (fmt::internal::is_negative(from)) {
+      ec = 1;
+      return {};
+    }
+
+    // From is positive. Can it always fit in To?
+    if (F::digits <= T::digits) {
+      // yes, From always fits in To.
+    } else {
+      // from may not fit in To, we have to do a dynamic check
+      if (from > static_cast<From>(T::max())) {
+        ec = 1;
+        return {};
+      }
+    }
+  }
+
+  if (!F::is_signed && T::is_signed) {
+    // can from be held in To?
+    if (F::digits < T::digits) {
+      // yes, From always fits in To.
+    } else {
+      // from may not fit in To, we have to do a dynamic check
+      if (from > static_cast<From>(T::max())) {
+        // outside range.
+        ec = 1;
+        return {};
+      }
+    }
+  }
+
+  // reaching here means all is ok for lossless conversion.
+  return static_cast<To>(from);
+
+}  // function
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(std::is_same<From, To>::value)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  return from;
+}  // function
+
+// clang-format off
+/**
+ * converts From to To if possible, otherwise ec is set.
+ *
+ * input                            |    output
+ * ---------------------------------|---------------
+ * NaN                              | NaN
+ * Inf                              | Inf
+ * normal, fits in output           | converted (possibly lossy)
+ * normal, does not fit in output   | ec is set
+ * subnormal                        | best effort
+ * -Inf                             | -Inf
+ */
+// clang-format on
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value)>
+FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+  ec = 0;
+  using T = std::numeric_limits<To>;
+  static_assert(std::is_floating_point<From>::value, "From must be floating");
+  static_assert(std::is_floating_point<To>::value, "To must be floating");
+
+  // catch the only happy case
+  if (std::isfinite(from)) {
+    if (from >= T::lowest() && from <= T::max()) {
+      return static_cast<To>(from);
+    }
+    // not within range.
+    ec = 1;
+    return {};
+  }
+
+  // nan and inf will be preserved
+  return static_cast<To>(from);
+}  // function
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(std::is_same<From, To>::value)>
+FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+  ec = 0;
+  static_assert(std::is_floating_point<From>::value, "From must be floating");
+  return from;
+}
+
+/**
+ * safe duration cast between integral durations
+ */
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_integral<FromRep>::value),
+          FMT_ENABLE_IF(std::is_integral<typename To::rep>::value)>
+To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                      int& ec) {
+  using From = std::chrono::duration<FromRep, FromPeriod>;
+  ec = 0;
+  // the basic idea is that we need to convert from count() in the from type
+  // to count() in the To type, by multiplying it with this:
+  struct Factor
+      : std::ratio_divide<typename From::period, typename To::period> {};
+
+  static_assert(Factor::num > 0, "num must be positive");
+  static_assert(Factor::den > 0, "den must be positive");
+
+  // the conversion is like this: multiply from.count() with Factor::num
+  // /Factor::den and convert it to To::rep, all this without
+  // overflow/underflow. let's start by finding a suitable type that can hold
+  // both To, From and Factor::num
+  using IntermediateRep =
+      typename std::common_type<typename From::rep, typename To::rep,
+                                decltype(Factor::num)>::type;
+
+  // safe conversion to IntermediateRep
+  IntermediateRep count =
+      lossless_integral_conversion<IntermediateRep>(from.count(), ec);
+  if (ec) {
+    return {};
+  }
+  // multiply with Factor::num without overflow or underflow
+  if (Factor::num != 1) {
+    const auto max1 = internal::max_value<IntermediateRep>() / Factor::num;
+    if (count > max1) {
+      ec = 1;
+      return {};
+    }
+    const auto min1 = std::numeric_limits<IntermediateRep>::min() / Factor::num;
+    if (count < min1) {
+      ec = 1;
+      return {};
+    }
+    count *= Factor::num;
+  }
+
+  // this can't go wrong, right? den>0 is checked earlier.
+  if (Factor::den != 1) {
+    count /= Factor::den;
+  }
+  // convert to the to type, safely
+  using ToRep = typename To::rep;
+  const ToRep tocount = lossless_integral_conversion<ToRep>(count, ec);
+  if (ec) {
+    return {};
+  }
+  return To{tocount};
+}
+
+/**
+ * safe duration_cast between floating point durations
+ */
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_floating_point<FromRep>::value),
+          FMT_ENABLE_IF(std::is_floating_point<typename To::rep>::value)>
+To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                      int& ec) {
+  using From = std::chrono::duration<FromRep, FromPeriod>;
+  ec = 0;
+  if (std::isnan(from.count())) {
+    // nan in, gives nan out. easy.
+    return To{std::numeric_limits<typename To::rep>::quiet_NaN()};
+  }
+  // maybe we should also check if from is denormal, and decide what to do about
+  // it.
+
+  // +-inf should be preserved.
+  if (std::isinf(from.count())) {
+    return To{from.count()};
+  }
+
+  // the basic idea is that we need to convert from count() in the from type
+  // to count() in the To type, by multiplying it with this:
+  struct Factor
+      : std::ratio_divide<typename From::period, typename To::period> {};
+
+  static_assert(Factor::num > 0, "num must be positive");
+  static_assert(Factor::den > 0, "den must be positive");
+
+  // the conversion is like this: multiply from.count() with Factor::num
+  // /Factor::den and convert it to To::rep, all this without
+  // overflow/underflow. let's start by finding a suitable type that can hold
+  // both To, From and Factor::num
+  using IntermediateRep =
+      typename std::common_type<typename From::rep, typename To::rep,
+                                decltype(Factor::num)>::type;
+
+  // force conversion of From::rep -> IntermediateRep to be safe,
+  // even if it will never happen be narrowing in this context.
+  IntermediateRep count =
+      safe_float_conversion<IntermediateRep>(from.count(), ec);
+  if (ec) {
+    return {};
+  }
+
+  // multiply with Factor::num without overflow or underflow
+  if (Factor::num != 1) {
+    constexpr auto max1 = internal::max_value<IntermediateRep>() /
+                          static_cast<IntermediateRep>(Factor::num);
+    if (count > max1) {
+      ec = 1;
+      return {};
+    }
+    constexpr auto min1 = std::numeric_limits<IntermediateRep>::lowest() /
+                          static_cast<IntermediateRep>(Factor::num);
+    if (count < min1) {
+      ec = 1;
+      return {};
+    }
+    count *= static_cast<IntermediateRep>(Factor::num);
+  }
+
+  // this can't go wrong, right? den>0 is checked earlier.
+  if (Factor::den != 1) {
+    using common_t = typename std::common_type<IntermediateRep, intmax_t>::type;
+    count /= static_cast<common_t>(Factor::den);
+  }
+
+  // convert to the to type, safely
+  using ToRep = typename To::rep;
+
+  const ToRep tocount = safe_float_conversion<ToRep>(count, ec);
+  if (ec) {
+    return {};
+  }
+  return To{tocount};
+}
+}  // namespace safe_duration_cast
+#endif
 
 // Prevents expansion of a preceding token as a function-style macro.
 // Usage: f FMT_NOMACRO()
diff --git a/include/fmt/safe-duration-cast.h b/include/fmt/safe-duration-cast.h
deleted file mode 100644
index 38aef69b..00000000
--- a/include/fmt/safe-duration-cast.h
+++ /dev/null
@@ -1,293 +0,0 @@
-/*
- * For conversion between std::chrono::durations without undefined
- * behaviour or erroneous results.
- * This is a stripped down version of duration_cast, for inclusion in fmt.
- * See https://github.com/pauldreik/safe_duration_cast
- *
- * Copyright Paul Dreik 2019
- *
- * This file is licensed under the fmt license, see format.h
- */
-
-#include <chrono>
-#include <cmath>
-#include <limits>
-#include <type_traits>
-
-#include "format.h"
-
-FMT_BEGIN_NAMESPACE
-
-namespace safe_duration_cast {
-
-template <typename To, typename From,
-          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
-                        std::numeric_limits<From>::is_signed ==
-                            std::numeric_limits<To>::is_signed)>
-FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
-  ec = 0;
-  using F = std::numeric_limits<From>;
-  using T = std::numeric_limits<To>;
-  static_assert(F::is_integer, "From must be integral");
-  static_assert(T::is_integer, "To must be integral");
-
-  // A and B are both signed, or both unsigned.
-  if (F::digits <= T::digits) {
-    // From fits in To without any problem.
-  } else {
-    // From does not always fit in To, resort to a dynamic check.
-    if (from < T::min() || from > T::max()) {
-      // outside range.
-      ec = 1;
-      return {};
-    }
-  }
-  return static_cast<To>(from);
-}
-
-/**
- * converts From to To, without loss. If the dynamic value of from
- * can't be converted to To without loss, ec is set.
- */
-template <typename To, typename From,
-          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
-                        std::numeric_limits<From>::is_signed !=
-                            std::numeric_limits<To>::is_signed)>
-FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
-  ec = 0;
-  using F = std::numeric_limits<From>;
-  using T = std::numeric_limits<To>;
-  static_assert(F::is_integer, "From must be integral");
-  static_assert(T::is_integer, "To must be integral");
-
-  if (F::is_signed && !T::is_signed) {
-    // From may be negative, not allowed!
-    if (fmt::internal::is_negative(from)) {
-      ec = 1;
-      return {};
-    }
-
-    // From is positive. Can it always fit in To?
-    if (F::digits <= T::digits) {
-      // yes, From always fits in To.
-    } else {
-      // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
-        ec = 1;
-        return {};
-      }
-    }
-  }
-
-  if (!F::is_signed && T::is_signed) {
-    // can from be held in To?
-    if (F::digits < T::digits) {
-      // yes, From always fits in To.
-    } else {
-      // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
-        // outside range.
-        ec = 1;
-        return {};
-      }
-    }
-  }
-
-  // reaching here means all is ok for lossless conversion.
-  return static_cast<To>(from);
-
-}  // function
-
-template <typename To, typename From,
-          FMT_ENABLE_IF(std::is_same<From, To>::value)>
-FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
-  ec = 0;
-  return from;
-}  // function
-
-// clang-format off
-/**
- * converts From to To if possible, otherwise ec is set.
- *
- * input                            |    output
- * ---------------------------------|---------------
- * NaN                              | NaN
- * Inf                              | Inf
- * normal, fits in output           | converted (possibly lossy)
- * normal, does not fit in output   | ec is set
- * subnormal                        | best effort
- * -Inf                             | -Inf
- */
-// clang-format on
-template <typename To, typename From,
-          FMT_ENABLE_IF(!std::is_same<From, To>::value)>
-FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
-  ec = 0;
-  using T = std::numeric_limits<To>;
-  static_assert(std::is_floating_point<From>::value, "From must be floating");
-  static_assert(std::is_floating_point<To>::value, "To must be floating");
-
-  // catch the only happy case
-  if (std::isfinite(from)) {
-    if (from >= T::lowest() && from <= T::max()) {
-      return static_cast<To>(from);
-    }
-    // not within range.
-    ec = 1;
-    return {};
-  }
-
-  // nan and inf will be preserved
-  return static_cast<To>(from);
-}  // function
-
-template <typename To, typename From,
-          FMT_ENABLE_IF(std::is_same<From, To>::value)>
-FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
-  ec = 0;
-  static_assert(std::is_floating_point<From>::value, "From must be floating");
-  return from;
-}
-
-/**
- * safe duration cast between integral durations
- */
-template <typename To, typename FromRep, typename FromPeriod,
-          FMT_ENABLE_IF(std::is_integral<FromRep>::value),
-          FMT_ENABLE_IF(std::is_integral<typename To::rep>::value)>
-To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
-                      int& ec) {
-  using From = std::chrono::duration<FromRep, FromPeriod>;
-  ec = 0;
-  // the basic idea is that we need to convert from count() in the from type
-  // to count() in the To type, by multiplying it with this:
-  struct Factor
-      : std::ratio_divide<typename From::period, typename To::period> {};
-
-  static_assert(Factor::num > 0, "num must be positive");
-  static_assert(Factor::den > 0, "den must be positive");
-
-  // the conversion is like this: multiply from.count() with Factor::num
-  // /Factor::den and convert it to To::rep, all this without
-  // overflow/underflow. let's start by finding a suitable type that can hold
-  // both To, From and Factor::num
-  using IntermediateRep =
-      typename std::common_type<typename From::rep, typename To::rep,
-                                decltype(Factor::num)>::type;
-
-  // safe conversion to IntermediateRep
-  IntermediateRep count =
-      lossless_integral_conversion<IntermediateRep>(from.count(), ec);
-  if (ec) {
-    return {};
-  }
-  // multiply with Factor::num without overflow or underflow
-  if (Factor::num != 1) {
-    const auto max1 = internal::max_value<IntermediateRep>() / Factor::num;
-    if (count > max1) {
-      ec = 1;
-      return {};
-    }
-    const auto min1 = std::numeric_limits<IntermediateRep>::min() / Factor::num;
-    if (count < min1) {
-      ec = 1;
-      return {};
-    }
-    count *= Factor::num;
-  }
-
-  // this can't go wrong, right? den>0 is checked earlier.
-  if (Factor::den != 1) {
-    count /= Factor::den;
-  }
-  // convert to the to type, safely
-  using ToRep = typename To::rep;
-  const ToRep tocount = lossless_integral_conversion<ToRep>(count, ec);
-  if (ec) {
-    return {};
-  }
-  return To{tocount};
-}
-
-/**
- * safe duration_cast between floating point durations
- */
-template <typename To, typename FromRep, typename FromPeriod,
-          FMT_ENABLE_IF(std::is_floating_point<FromRep>::value),
-          FMT_ENABLE_IF(std::is_floating_point<typename To::rep>::value)>
-To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
-                      int& ec) {
-  using From = std::chrono::duration<FromRep, FromPeriod>;
-  ec = 0;
-  if (std::isnan(from.count())) {
-    // nan in, gives nan out. easy.
-    return To{std::numeric_limits<typename To::rep>::quiet_NaN()};
-  }
-  // maybe we should also check if from is denormal, and decide what to do about
-  // it.
-
-  // +-inf should be preserved.
-  if (std::isinf(from.count())) {
-    return To{from.count()};
-  }
-
-  // the basic idea is that we need to convert from count() in the from type
-  // to count() in the To type, by multiplying it with this:
-  struct Factor
-      : std::ratio_divide<typename From::period, typename To::period> {};
-
-  static_assert(Factor::num > 0, "num must be positive");
-  static_assert(Factor::den > 0, "den must be positive");
-
-  // the conversion is like this: multiply from.count() with Factor::num
-  // /Factor::den and convert it to To::rep, all this without
-  // overflow/underflow. let's start by finding a suitable type that can hold
-  // both To, From and Factor::num
-  using IntermediateRep =
-      typename std::common_type<typename From::rep, typename To::rep,
-                                decltype(Factor::num)>::type;
-
-  // force conversion of From::rep -> IntermediateRep to be safe,
-  // even if it will never happen be narrowing in this context.
-  IntermediateRep count =
-      safe_float_conversion<IntermediateRep>(from.count(), ec);
-  if (ec) {
-    return {};
-  }
-
-  // multiply with Factor::num without overflow or underflow
-  if (Factor::num != 1) {
-    constexpr auto max1 = internal::max_value<IntermediateRep>() /
-                          static_cast<IntermediateRep>(Factor::num);
-    if (count > max1) {
-      ec = 1;
-      return {};
-    }
-    constexpr auto min1 = std::numeric_limits<IntermediateRep>::lowest() /
-                          static_cast<IntermediateRep>(Factor::num);
-    if (count < min1) {
-      ec = 1;
-      return {};
-    }
-    count *= static_cast<IntermediateRep>(Factor::num);
-  }
-
-  // this can't go wrong, right? den>0 is checked earlier.
-  if (Factor::den != 1) {
-    using common_t = typename std::common_type<IntermediateRep, intmax_t>::type;
-    count /= static_cast<common_t>(Factor::den);
-  }
-
-  // convert to the to type, safely
-  using ToRep = typename To::rep;
-
-  const ToRep tocount = safe_float_conversion<ToRep>(count, ec);
-  if (ec) {
-    return {};
-  }
-  return To{tocount};
-}
-
-}  // namespace safe_duration_cast
-
-FMT_END_NAMESPACE