diff --git a/test/tz_test/OffsetZone.h b/test/tz_test/OffsetZone.h
new file mode 100644
index 0000000..bacb03c
--- /dev/null
+++ b/test/tz_test/OffsetZone.h
@@ -0,0 +1,73 @@
+#ifndef OFFSET_ZONE_H
+#define OFFSET_ZONE_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2017 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// Test custom time zone support
+
+#include "tz.h"
+
+class OffsetZone
+{
+    std::chrono::minutes offset_;
+
+public:
+    explicit OffsetZone(std::chrono::minutes offset)
+        : offset_{offset}
+        {}
+
+    template <class Duration>
+        auto
+        to_local(date::sys_time<Duration> tp) const
+        {
+            using namespace date;
+            using namespace std::chrono;
+            using LT = local_time<std::common_type_t<Duration, minutes>>;
+            return LT{(tp + offset_).time_since_epoch()};
+        }
+
+    template <class Duration>
+        auto
+        to_sys(date::local_time<Duration> tp, date::choose = date::choose::earliest) const
+        {
+            using namespace date;
+            using namespace std::chrono;
+            using ST = sys_time<std::common_type_t<Duration, minutes>>;
+            return ST{(tp - offset_).time_since_epoch()};
+        }
+
+    template <class Duration>
+        date::sys_info
+        get_info(date::sys_time<Duration> st) const
+        {
+            using namespace date;
+            using namespace std::chrono;
+            return {sys_seconds::min(), sys_seconds::max(), offset_,
+                    minutes{0}, offset_ >= minutes{0} ? "+" + date::format("%H%M", offset_)
+                                          : "-" + date::format("%H%M", -offset_)};
+        }
+
+    const OffsetZone* operator->() const {return this;}
+};
+
+#endif // OFFSET_ZONE_H
diff --git a/test/tz_test/OffsetZone.pass.cpp b/test/tz_test/OffsetZone.pass.cpp
index b0f9e23..0cef837 100644
--- a/test/tz_test/OffsetZone.pass.cpp
+++ b/test/tz_test/OffsetZone.pass.cpp
@@ -23,50 +23,7 @@
 // Test custom time zone support
 
 #include "tz.h"
-
-class OffsetZone
-{
-    std::chrono::minutes offset_;
-
-public:
-    explicit OffsetZone(std::chrono::minutes offset)
-        : offset_{offset}
-        {}
-
-    template <class Duration>
-        auto
-        to_local(date::sys_time<Duration> tp) const
-        {
-            using namespace date;
-            using namespace std::chrono;
-            using LT = local_time<std::common_type_t<Duration, minutes>>;
-            return LT{(tp + offset_).time_since_epoch()};
-        }
-
-    template <class Duration>
-        auto
-        to_sys(date::local_time<Duration> tp) const
-        {
-            using namespace date;
-            using namespace std::chrono;
-            using ST = sys_time<std::common_type_t<Duration, minutes>>;
-            return ST{(tp - offset_).time_since_epoch()};
-        }
-
-    template <class Duration>
-        date::sys_info
-        get_info(date::sys_time<Duration> st) const
-        {
-            using namespace date;
-            using namespace std::chrono;
-            return {sys_seconds::min(), sys_seconds::max(), offset_,
-                    minutes{0}, offset_ >= minutes{0} ? "+" + date::format("%H%M", offset_)
-                                          : "-" + date::format("%H%M", -offset_)};
-        }
-
-    const OffsetZone* operator->() const {return this;}
-};
-
+#include "OffsetZone.h"
 #include <cassert>
 
 int
diff --git a/test/tz_test/zoned_time_deduction.pass.cpp b/test/tz_test/zoned_time_deduction.pass.cpp
index d57c226..8cf4440 100644
--- a/test/tz_test/zoned_time_deduction.pass.cpp
+++ b/test/tz_test/zoned_time_deduction.pass.cpp
@@ -21,6 +21,7 @@
 // SOFTWARE.
 
 #include "tz.h"
+#include "OffsetZone.h"
 #include <cassert>
 #include <type_traits>
 #include <string>
@@ -216,5 +217,13 @@ main()
        testDeductionFrom<time_zone const*>(std::move(tz));
     }
 
+    // custom time zone
+    {
+       OffsetZone tz(minutes(45));
+       testDeductionFrom<OffsetZone>(tz);
+       testDeductionFrom<OffsetZone>(to_const(tz));
+       testDeductionFrom<OffsetZone>(std::move(tz));
+    }
+
 #endif  // HAS_DEDUCTION_GUIDES
 }