DateTime: add default constructor (#1220)

sdk/core/azure-core/CHANGELOG.md

@@ -5,9 +5,10 @@
 ### New Features
 
 - Added a WinHTTP-based `HttpTransport` called `WinHttpTransport` and use that as the default `TransportPolicyOptions.Transport` on Windows when sending and receiving requests and responses over the wire.
-- Added `Range` type to `Azure::Core::Http` namespace. 
+- Added `Range` type to `Azure::Core::Http` namespace.
 - Added support for long-running operations with `Operation<T>`.
 - Added support for setting a custom transport adapter by implementing the method `std::shared_ptr<HttpTransport> ::AzureSdkGetCustomHttpTransport()`.
+- Added default constructor to `DateTime`.
 
 ### Breaking Changes
 

sdk/core/azure-core/inc/azure/core/datetime.hpp

@@ -227,5 +227,11 @@ namespace Azure { namespace Core {
     // Private constructor. Use static methods to create an instance.
     explicit DateTime(Duration const& since1601) : m_since1601(since1601) {}
     Duration m_since1601;
+
+  public:
+    /**
+     * @brief Construct an instance of @DateTime.
+     */
+    DateTime() : m_since1601(0) {}
   };
 }} // namespace Azure::Core

sdk/core/azure-core/test/ut/datetime.cpp

@@ -578,3 +578,9 @@ TEST(DateTime, ArithmeticOperators)
   dt3 = dt2 - 24h;
   EXPECT_EQ(dt3, dt1);
 }
+
+TEST(DateTime, DefaultConstructible)
+{
+  DateTime dt;
+  EXPECT_EQ(0, (dt - Year1601).count());
+}