diff --git a/ChangeLog b/ChangeLog
index 2020ef11..2c963942 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2010-10-26  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	Use std::numeric_limits<time_t> instead of checking of
+	sizeof(time_t).
+	* src/NsCookieParser.cc
+	* src/Sqlite3CookieParser.cc
+	* src/cookie_helper.cc
+	* test/CookieHelperTest.cc
+	* test/CookieStorageTest.cc
+	* test/NsCookieParserTest.cc
+
 2010-10-26  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Fixed improper use of vsnprintf
diff --git a/src/NsCookieParser.cc b/src/NsCookieParser.cc
index 1a4f13ed..9d3c3c1b 100644
--- a/src/NsCookieParser.cc
+++ b/src/NsCookieParser.cc
@@ -35,6 +35,7 @@
 #include "NsCookieParser.h"
 
 #include <fstream>
+#include <limits>
 
 #include "util.h"
 #include "A2STR.h"
@@ -70,12 +71,15 @@ bool parseNsCookie
   if(!util::parseLLIntNoThrow(expiryTime, vs[4])) {
     return false;
   }
-  if(sizeof(time_t) == 4 && expiryTime > INT32_MAX) {
-    expiryTime = INT32_MAX;
+  if(std::numeric_limits<time_t>::max() < expiryTime) {
+    expiryTime = std::numeric_limits<time_t>::max();
+  } else if(std::numeric_limits<time_t>::min() > expiryTime) {
+    expiryTime = std::numeric_limits<time_t>::min();
   }
   cookie.setName(vs[5]);
   cookie.setValue(vs.size() >= 7? vs[6]:A2STR::NIL);
-  cookie.setExpiryTime(expiryTime == 0?INT32_MAX:expiryTime);
+  cookie.setExpiryTime(expiryTime == 0?
+                       std::numeric_limits<time_t>::max():expiryTime);
   // aria2 treats expiryTime == 0 means session cookie.
   cookie.setPersistent(expiryTime != 0);
   cookie.setDomain(cookieDomain);
diff --git a/src/Sqlite3CookieParser.cc b/src/Sqlite3CookieParser.cc
index 088ff99a..0a6ae9f9 100644
--- a/src/Sqlite3CookieParser.cc
+++ b/src/Sqlite3CookieParser.cc
@@ -35,6 +35,7 @@
 #include "Sqlite3CookieParser.h"
 
 #include <cstring>
+#include <limits>
 
 #include "DlAbortEx.h"
 #include "util.h"
@@ -83,8 +84,10 @@ static bool parseTime(int64_t& time, const std::string& s)
   if(!util::parseLLIntNoThrow(time, s)) {
     return false;
   }
-  if(sizeof(time_t) == 4 && time > INT32_MAX) {
-    time = INT32_MAX;
+  if(std::numeric_limits<time_t>::max() < time) {
+    time = std::numeric_limits<time_t>::max();
+  } else if(std::numeric_limits<time_t>::min() > time) {
+    time = std::numeric_limits<time_t>::min();
   }
   return true;
 }
diff --git a/src/cookie_helper.cc b/src/cookie_helper.cc
index d1cdbc73..69b2366f 100644
--- a/src/cookie_helper.cc
+++ b/src/cookie_helper.cc
@@ -36,6 +36,7 @@
 
 #include <cstring>
 #include <vector>
+#include <limits>
 
 #include "util.h"
 #include "array_fun.h"
@@ -263,8 +264,8 @@ bool parse
         } else {
           int64_t n = creationTime;
           n += delta;
-          if(n < 0 || (sizeof(time_t) < 8 && n > INT32_MAX)) {
-            maxAge = INT32_MAX;
+          if(n < 0 || std::numeric_limits<time_t>::max() < n) {
+            maxAge = std::numeric_limits<time_t>::max();
           } else {
             maxAge = n;
           }
@@ -302,7 +303,7 @@ bool parse
   } else if(foundExpires) {
     persistent = true;
   } else {
-    expiryTime = INT32_MAX;
+    expiryTime = std::numeric_limits<time_t>::max();
     persistent = false;
   }
 
diff --git a/test/CookieHelperTest.cc b/test/CookieHelperTest.cc
index cca16382..35d81a1c 100644
--- a/test/CookieHelperTest.cc
+++ b/test/CookieHelperTest.cc
@@ -1,5 +1,7 @@
 #include "cookie_helper.h"
 
+#include <limits>
+
 #include <cppunit/extensions/HelperMacros.h>
 
 #include "Exception.h"
@@ -123,7 +125,7 @@ void CookieHelperTest::testParse()
     std::string str = "id=; Max-Age=9223372036854775807;";
     Cookie c;
     CPPUNIT_ASSERT(cookie::parse(c, str, "localhost", "/", creationDate));
-    CPPUNIT_ASSERT_EQUAL((time_t)INT32_MAX, c.getExpiryTime());
+    CPPUNIT_ASSERT_EQUAL(std::numeric_limits<time_t>::max(), c.getExpiryTime());
     CPPUNIT_ASSERT(c.getPersistent());
   }
   {
diff --git a/test/CookieStorageTest.cc b/test/CookieStorageTest.cc
index 58c1c73e..f8ec0b0c 100644
--- a/test/CookieStorageTest.cc
+++ b/test/CookieStorageTest.cc
@@ -2,6 +2,7 @@
 
 #include <iostream>
 #include <algorithm>
+#include <limits>
 
 #include <cppunit/extensions/HelperMacros.h>
 
@@ -269,7 +270,7 @@ void CookieStorageTest::testLoad()
   Cookie c = cookies[0];
   CPPUNIT_ASSERT_EQUAL(std::string("passwd"), c.getName());
   CPPUNIT_ASSERT_EQUAL(std::string("secret"), c.getValue());
-  CPPUNIT_ASSERT_EQUAL((time_t)INT32_MAX, c.getExpiryTime());
+  CPPUNIT_ASSERT_EQUAL(std::numeric_limits<time_t>::max(), c.getExpiryTime());
   CPPUNIT_ASSERT(!c.getPersistent());
   CPPUNIT_ASSERT_EQUAL(std::string("/cgi-bin"), c.getPath());
   CPPUNIT_ASSERT_EQUAL(std::string("192.168.0.1"), c.getDomain());
diff --git a/test/NsCookieParserTest.cc b/test/NsCookieParserTest.cc
index fd5fbd31..1e431d2b 100644
--- a/test/NsCookieParserTest.cc
+++ b/test/NsCookieParserTest.cc
@@ -1,6 +1,7 @@
 #include "NsCookieParser.h"
 
 #include <iostream>
+#include <limits>
 
 #include <cppunit/extensions/HelperMacros.h>
 
@@ -58,7 +59,7 @@ void NsCookieParserTest::testParse()
   c = cookies[2];
   CPPUNIT_ASSERT_EQUAL(std::string("passwd"), c.getName());
   CPPUNIT_ASSERT_EQUAL(std::string("secret"), c.getValue());
-  CPPUNIT_ASSERT_EQUAL((time_t)INT32_MAX, c.getExpiryTime());
+  CPPUNIT_ASSERT_EQUAL(std::numeric_limits<time_t>::max(), c.getExpiryTime());
   CPPUNIT_ASSERT(!c.getPersistent());
   CPPUNIT_ASSERT_EQUAL(std::string("192.168.0.1"), c.getDomain());
   CPPUNIT_ASSERT(c.getHostOnly());