diff --git a/include/ndn-cpp/security/certificate/certificate.hpp b/include/ndn-cpp/security/certificate/certificate.hpp
index 21745e2..bc6b355 100644
--- a/include/ndn-cpp/security/certificate/certificate.hpp
+++ b/include/ndn-cpp/security/certificate/certificate.hpp
@@ -61,21 +61,21 @@
   addExtension(const CertificateExtension& extension) { extensionList_.push_back(extension); }
 
   void 
-  setNotBefore(const Time& notBefore) { notBefore_ = notBefore; }
+  setNotBefore(const MillisecondsSince1970& notBefore) { notBefore_ = notBefore; }
 
-  Time& 
+  MillisecondsSince1970& 
   getNotBefore() { return notBefore_; }
   
-  const Time& 
+  const MillisecondsSince1970& 
   getNotBefore() const { return notBefore_; }
 
   void
-  setNotAfter(const Time& notAfter) { notAfter_ = notAfter; }
+  setNotAfter(const MillisecondsSince1970& notAfter) { notAfter_ = notAfter; }
 
-  Time& 
+  MillisecondsSince1970& 
   getNotAfter() { return notAfter_; }
 
-  const Time& 
+  const MillisecondsSince1970& 
   getNotAfter() const { return notAfter_; }
 
   void
@@ -113,8 +113,8 @@
 
 protected:
   SubjectDescriptionList subjectDescriptionList_;
-  Time notBefore_;
-  Time notAfter_;
+  MillisecondsSince1970 notBefore_;
+  MillisecondsSince1970 notAfter_;
   PublicKey key_;
   ExtensionList extensionList_;
 };
diff --git a/include/ndn-cpp/security/identity/basic-identity-storage.hpp b/include/ndn-cpp/security/identity/basic-identity-storage.hpp
index ee1a886..d841548 100644
--- a/include/ndn-cpp/security/identity/basic-identity-storage.hpp
+++ b/include/ndn-cpp/security/identity/basic-identity-storage.hpp
@@ -200,7 +200,7 @@
 
   sqlite3 *database_;
 #if 0
-  Time lastUpdated_;
+  MillisecondsSince1970 lastUpdated_;
 #endif
 };
 
diff --git a/include/ndn-cpp/security/identity/identity-manager.hpp b/include/ndn-cpp/security/identity/identity-manager.hpp
index d31e214..1d6df04 100644
--- a/include/ndn-cpp/security/identity/identity-manager.hpp
+++ b/include/ndn-cpp/security/identity/identity-manager.hpp
@@ -106,7 +106,7 @@
    * @return The name of generated identity certificate.
    */
   Name
-  createIdentityCertificate(const Name& keyName, const Name& signerCertificateName, const Time& notBefore, const Time& notAfter);
+  createIdentityCertificate(const Name& keyName, const Name& signerCertificateName, const MillisecondsSince1970& notBefore, const MillisecondsSince1970& notAfter);
 
   /**
    * Create an identity certificate for a public key supplied by the caller.
@@ -119,7 +119,7 @@
    */
   ptr_lib::shared_ptr<IdentityCertificate>
   createIdentityCertificate
-    (const Name& keyName, const PublicKey& publickey, const Name& signerCertificateName, const Time& notBefore, const Time& notAfter); 
+    (const Name& keyName, const PublicKey& publickey, const Name& signerCertificateName, const MillisecondsSince1970& notBefore, const MillisecondsSince1970& notAfter); 
     
   /**
    * Add a certificate into the public key identity storage.