diff --git a/source/datetime.cpp b/source/datetime.cpp
index 8b024735..e6e8fa5b 100644
--- a/source/datetime.cpp
+++ b/source/datetime.cpp
@@ -14,29 +14,28 @@
 #if defined(NANA_WINDOWS)
 	#include <windows.h>
 #endif
-#include <cassert>
 #include <array>
 
 namespace {
 	std::tm localtime()
 	{
 #if defined(NANA_WINDOWS) && !defined(NANA_MINGW)
-		time_t t;
-		::time(&t);
+		std::time_t t = std::time(nullptr);
 		std::tm tm;
-		if(localtime_s(&tm, &t) != 0)
-			assert(false);
+		if (localtime_s(&tm, &t) != 0)
+			throw std::runtime_error("invalid local time");
 
 		return tm;
 #else
 		time_t t = std::time(nullptr);
 		struct tm * tm_addr = std::localtime(&t);
-		assert(tm_addr);
-		
+		if(nullptr == tm_addr)
+			throw std::runtime_error("invalid local time");
+
 		return *tm_addr;
 #endif
 	}
-	
+
 	::nana::date::value to_dateval(const std::tm& t)
 	{
 		return {static_cast<unsigned>(t.tm_year + 1900), static_cast<unsigned>(t.tm_mon + 1), static_cast<unsigned>(t.tm_mday)};
@@ -51,7 +50,7 @@ namespace {
 
 namespace nana
 {
-	//class date		
+	//class date
 		void date::set(const std::tm& t)
 		{
 			value_ = to_dateval(t);
diff --git a/source/gui/place.cpp b/source/gui/place.cpp
index b29d98b0..b9acf02e 100644
--- a/source/gui/place.cpp
+++ b/source/gui/place.cpp
@@ -617,7 +617,7 @@ namespace nana
 
 				: std::invalid_argument{ what + " from place implementation " },
 				  pos{ pos },
-				  field { field.empty() ? "unnamed" : field }
+				  field(field.empty() ? "unnamed" : field)
 			{}
 			std::string::size_type pos;
 			std::string            field;
@@ -3674,18 +3674,18 @@ namespace nana
 						std::string field,
 						std::string::size_type pos)
 
-		: std::invalid_argument{  "from widget '" 
+		: std::invalid_argument(  "from widget '" 
 		                        + API::window_caption(plc.window_handle()).substr(0,80)
 								+ "'; nana::place error "
 		                        + what 
 		                        + "' in field '" + field
 								+ (pos == std::string::npos ? "' " : "' at position " + std::to_string(pos))
-								+ " in div_text:\n" + plc.div() },
-		base_what{ what },
-		owner_caption{ API::window_caption(plc.window_handle()).substr(0,80) },
-		div_text{ plc.div() },
-		field{ field },
-		pos{ pos }
+								+ " in div_text:\n" + plc.div() ),
+		base_what( what ),
+		owner_caption( API::window_caption(plc.window_handle()).substr(0,80) ),
+		div_text( plc.div() ),
+		field( field ),
+		pos( pos )
 	{}
 	//end class place
 
diff --git a/source/system/dataexch.cpp b/source/system/dataexch.cpp
index 8c25ed5e..b3f4d5d4 100644
--- a/source/system/dataexch.cpp
+++ b/source/system/dataexch.cpp
@@ -15,7 +15,6 @@
 #include <nana/paint/graphics.hpp>
 #include <nana/paint/pixel_buffer.hpp>
 #include <vector>
-#include <cassert>
 #include <cstring>
 
 #if defined(NANA_WINDOWS)
@@ -71,7 +70,6 @@ namespace nana{ namespace system{
 			bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
 			HDC hDC = ::GetDC(NULL);
 			if (::GetDIBits(hDC, (HBITMAP)g.pixmap(), 0, 1, NULL, (BITMAPINFO *)&bmi, DIB_RGB_COLORS) == 0) {
-				assert(false);
 				::ReleaseDC(NULL, hDC);
 				return false;
 			}
@@ -109,7 +107,6 @@ namespace nana{ namespace system{
 						::CloseClipboard();
 					}
 			}
-			assert(false);
 			::GlobalFree(h_gmem);
 			return false;