diff --git a/examples/client_basics.cc b/examples/client_basics.cc
index 62b314d..d5a6fb7 100644
--- a/examples/client_basics.cc
+++ b/examples/client_basics.cc
@@ -31,6 +31,7 @@ int main() {
                              Url("http://httpbin.org/get").
                              Query("key1", "value1").
                              Query("key2", "value2").
+                             Date().
                              Header("Accept", "application/json")
                              ());
 
diff --git a/unittest/utility_unittest.cc b/unittest/utility_unittest.cc
index 4e16d83..dae3b84 100644
--- a/unittest/utility_unittest.cc
+++ b/unittest/utility_unittest.cc
@@ -8,7 +8,7 @@ TEST(UtilityTest, SplitKV) {
   std::string key;
   std::string value;
 
-  bool ok = webcc::SplitKV(str, ':', &key, &value);
+  bool ok = webcc::utility::SplitKV(str, ':', &key, &value);
 
   EXPECT_EQ(true, ok);
   EXPECT_EQ("Connection", key);
diff --git a/webcc/client_session.cc b/webcc/client_session.cc
index bb65d5a..5e5fc05 100644
--- a/webcc/client_session.cc
+++ b/webcc/client_session.cc
@@ -3,6 +3,7 @@
 #include "webcc/base64.h"
 #include "webcc/logger.h"
 #include "webcc/url.h"
+#include "webcc/utility.h"
 
 namespace webcc {
 
@@ -124,7 +125,7 @@ ResponsePtr ClientSession::Patch(const std::string& url, std::string&& data,
 void ClientSession::InitHeaders() {
   using namespace headers;
 
-  headers_.Set(kUserAgent, UserAgent());
+  headers_.Set(kUserAgent, utility::UserAgent());
 
   // Content-Encoding Tokens:
   //   (https://en.wikipedia.org/wiki/HTTP_compression)
diff --git a/webcc/common.cc b/webcc/common.cc
index c754672..f1e23af 100644
--- a/webcc/common.cc
+++ b/webcc/common.cc
@@ -98,7 +98,7 @@ std::vector<Header>::iterator Headers::Find(const std::string& key) {
 static bool ParseValue(const std::string& str, const std::string& expected_key,
                        std::string* value) {
   std::string key;
-  if (!SplitKV(str, '=', &key, value)) {
+  if (!utility::SplitKV(str, '=', &key, value)) {
     return false;
   }
 
@@ -182,7 +182,7 @@ bool ContentDisposition::Init(const std::string& str) {
   std::string key;
   std::string value;
   for (std::size_t i = 1; i < parts.size(); ++i) {
-    if (!SplitKV(parts[i], '=', &key, &value)) {
+    if (!utility::SplitKV(parts[i], '=', &key, &value)) {
       return false;
     }
 
diff --git a/webcc/globals.cc b/webcc/globals.cc
index dd33279..7402187 100644
--- a/webcc/globals.cc
+++ b/webcc/globals.cc
@@ -8,11 +8,6 @@ namespace webcc {
 
 // -----------------------------------------------------------------------------
 
-const std::string& UserAgent() {
-  static std::string s_user_agent = std::string("Webcc/") + WEBCC_VERSION;
-  return s_user_agent;
-}
-
 namespace media_types {
 
 // TODO: Add more.
diff --git a/webcc/globals.h b/webcc/globals.h
index 24efe10..4e0e14b 100644
--- a/webcc/globals.h
+++ b/webcc/globals.h
@@ -38,8 +38,6 @@
 
 #endif  // _MSC_VER
 
-#define ARRAY_SIZE(A) (sizeof(A) / sizeof(*(A)))
-
 namespace webcc {
 
 // -----------------------------------------------------------------------------
@@ -149,9 +147,6 @@ enum class ContentEncoding {
   kDeflate,
 };
 
-// Return default user agent for HTTP headers.
-const std::string& UserAgent();
-
 // -----------------------------------------------------------------------------
 
 // Client side error codes.
diff --git a/webcc/gzip.cc b/webcc/gzip.cc
index ed18281..28489e2 100644
--- a/webcc/gzip.cc
+++ b/webcc/gzip.cc
@@ -49,7 +49,7 @@ bool Compress(const std::string& input, std::string* output) {
     }
 
     std::size_t size = buf.size() - stream.avail_out;
-    output->insert(output->end(), buf.data(), buf.data() + size);
+    output->append(buf.data(), size);
 
   } while (stream.avail_out == 0);
 
@@ -106,6 +106,7 @@ bool Decompress(const std::string& input, std::string* output) {
     if (err == Z_STREAM_END) {
       break;
     }
+
     if (err != Z_OK) {
       inflateEnd(&stream);
       if (stream.msg != nullptr) {
diff --git a/webcc/message.cc b/webcc/message.cc
index 9a9d0d8..80cc9aa 100644
--- a/webcc/message.cc
+++ b/webcc/message.cc
@@ -1,7 +1,5 @@
 #include "webcc/message.h"
 
-#include <ctime>
-#include <iomanip>  // for put_time
 #include <sstream>
 
 #include "boost/algorithm/string.hpp"
@@ -181,11 +179,4 @@ std::string Message::Dump(std::size_t indent,
   return ss.str();
 }
 
-std::string Message::GetTimestamp() {
-  std::time_t t = std::time(nullptr);
-  std::stringstream ss;
-  ss << std::put_time(std::gmtime(&t), "%a, %d %b %Y %H:%M:%S") << " GMT";
-  return ss.str();
-}
-
 }  // namespace webcc
diff --git a/webcc/message.h b/webcc/message.h
index f8e2983..07387ad 100644
--- a/webcc/message.h
+++ b/webcc/message.h
@@ -112,11 +112,6 @@ protected:
     SetHeader(headers::kContentLength, std::to_string(content_length));
   }
 
-  // Get the timestamp for HTTP Date header field.
-  // E.g., Wed, 21 Oct 2015 07:28:00 GMT
-  // See: https://tools.ietf.org/html/rfc7231#section-7.1.1.2
-  std::string GetTimestamp();
-
 protected:
   std::string start_line_;
 
diff --git a/webcc/parser.cc b/webcc/parser.cc
index 8c5c575..f4aca5c 100644
--- a/webcc/parser.cc
+++ b/webcc/parser.cc
@@ -138,7 +138,7 @@ bool Parser::GetNextLine(std::size_t off, std::string* line, bool erase) {
 
 bool Parser::ParseHeaderLine(const std::string& line) {
   Header header;
-  if (!SplitKV(line, ':', &header.first, &header.second)) {
+  if (!utility::SplitKV(line, ':', &header.first, &header.second)) {
     LOG_ERRO("Invalid header: %s", line.c_str());
     return false;
   }
diff --git a/webcc/request.cc b/webcc/request.cc
index 15f94f7..bb143bc 100644
--- a/webcc/request.cc
+++ b/webcc/request.cc
@@ -37,7 +37,7 @@ void Request::Prepare() {
   // Another choice to generate the boundary is like what Apache does.
   // See: https://stackoverflow.com/a/5686863
   if (boundary_.empty()) {
-    boundary_ = RandomUuid();
+    boundary_ = utility::RandomUuid();
   }
 
   SetContentType("multipart/form-data; boundary=" + boundary_);
diff --git a/webcc/request_builder.cc b/webcc/request_builder.cc
index ad15f37..4442cd4 100644
--- a/webcc/request_builder.cc
+++ b/webcc/request_builder.cc
@@ -78,6 +78,12 @@ RequestBuilder& RequestBuilder::AuthToken(const std::string& token) {
   return Auth("Token", token);
 }
 
+RequestBuilder& RequestBuilder::Date() {
+  headers_.push_back(headers::kDate);
+  headers_.push_back(utility::GetTimestamp());
+  return *this;
+}
+
 void RequestBuilder::SetContent(RequestPtr request, std::string&& data) {
 #if WEBCC_ENABLE_GZIP
   if (gzip_ && data.size() > kGzipThreshold) {
diff --git a/webcc/request_builder.h b/webcc/request_builder.h
index d592726..0d75d51 100644
--- a/webcc/request_builder.h
+++ b/webcc/request_builder.h
@@ -96,6 +96,9 @@ public:
 
   RequestBuilder& AuthToken(const std::string& token);
 
+  // Add the Date header to the request.
+  RequestBuilder& Date();
+
 private:
   void SetContent(RequestPtr request, std::string&& data);
   
diff --git a/webcc/request_parser.cc b/webcc/request_parser.cc
index 9571a0d..00295f1 100644
--- a/webcc/request_parser.cc
+++ b/webcc/request_parser.cc
@@ -167,7 +167,7 @@ bool RequestParser::ParsePartHeaders(bool* need_more_data) {
     }
 
     Header header;
-    if (!SplitKV(line, ':', &header.first, &header.second)) {
+    if (!utility::SplitKV(line, ':', &header.first, &header.second)) {
       LOG_ERRO("Invalid part header line: %s", line.c_str());
       return false;
     }
diff --git a/webcc/response.cc b/webcc/response.cc
index 8d127a1..d299c6b 100644
--- a/webcc/response.cc
+++ b/webcc/response.cc
@@ -1,12 +1,14 @@
 #include "webcc/response.h"
 
+#include "webcc/utility.h"
+
 namespace webcc {
 
 void Response::Prepare() {
   PrepareStatusLine();
 
-  SetHeader(headers::kServer, UserAgent());
-  SetHeader(headers::kDate, GetTimestamp());
+  SetHeader(headers::kServer, utility::UserAgent());
+  SetHeader(headers::kDate, utility::GetTimestamp());
 
   Message::Prepare();
 }
diff --git a/webcc/utility.cc b/webcc/utility.cc
index 0d97c7c..0edfac3 100644
--- a/webcc/utility.cc
+++ b/webcc/utility.cc
@@ -1,12 +1,17 @@
 #include "webcc/utility.h"
 
+#include <ctime>
+#include <iomanip>  // for put_time
 #include <sstream>
 
 #include "boost/algorithm/string.hpp"
 #include "boost/uuid/random_generator.hpp"
 #include "boost/uuid/uuid_io.hpp"
 
+#include "webcc/version.h"
+
 namespace webcc {
+namespace utility {
 
 std::string RandomUuid() {
   boost::uuids::uuid u = boost::uuids::random_generator()();
@@ -15,6 +20,18 @@ std::string RandomUuid() {
   return ss.str();
 }
 
+const std::string& UserAgent() {
+  static auto s_user_agent = std::string("Webcc/") + WEBCC_VERSION;
+  return s_user_agent;
+}
+
+std::string GetTimestamp() {
+  std::time_t t = std::time(nullptr);
+  std::stringstream ss;
+  ss << std::put_time(std::gmtime(&t), "%a, %d %b %Y %H:%M:%S") << " GMT";
+  return ss.str();
+}
+
 bool SplitKV(const std::string& str, char delimiter,
              std::string* part1, std::string* part2) {
   std::size_t pos = str.find(delimiter);
@@ -31,4 +48,5 @@ bool SplitKV(const std::string& str, char delimiter,
   return true;
 }
 
+}  // namespace utility
 }  // namespace webcc
diff --git a/webcc/utility.h b/webcc/utility.h
index 37283e0..01a89f3 100644
--- a/webcc/utility.h
+++ b/webcc/utility.h
@@ -4,14 +4,25 @@
 #include <string>
 
 namespace webcc {
+namespace utility {
 
+// Get a randomly generated UUID.
 std::string RandomUuid();
 
+// Get default user agent for HTTP headers.
+const std::string& UserAgent();
+
+// Get the timestamp for HTTP Date header field.
+// E.g., Wed, 21 Oct 2015 07:28:00 GMT
+// See: https://tools.ietf.org/html/rfc7231#section-7.1.1.2
+std::string GetTimestamp();
+
 // Split a key-value string.
 // E.g., split "Connection: Keep-Alive".
 bool SplitKV(const std::string& str, char delimiter,
              std::string* key, std::string* value);
 
+}  // namespace utility
 }  // namespace webcc
 
 #endif  // WEBCC_UTILITY_H_