diff --git a/src/security/v2/certificate-cache.cpp b/src/security/v2/certificate-cache.cpp
index be2b084..9726b7e 100644
--- a/src/security/v2/certificate-cache.cpp
+++ b/src/security/v2/certificate-cache.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -28,11 +28,10 @@
 
 NDN_LOG_INIT(ndn.security.v2.CertificateCache);
 
-const time::nanoseconds&
+time::nanoseconds
 CertificateCache::getDefaultLifetime()
 {
-  static time::nanoseconds lifetime = time::seconds(3600);
-  return lifetime;
+  return 1_h;
 }
 
 CertificateCache::CertificateCache(const time::nanoseconds& maxLifetime)
diff --git a/src/security/v2/certificate-cache.hpp b/src/security/v2/certificate-cache.hpp
index a5109a8..53157b4 100644
--- a/src/security/v2/certificate-cache.hpp
+++ b/src/security/v2/certificate-cache.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -118,7 +118,7 @@
   refresh();
 
 public:
-  static const time::nanoseconds&
+  static time::nanoseconds
   getDefaultLifetime();
 
 private:
diff --git a/src/security/v2/certificate-storage.cpp b/src/security/v2/certificate-storage.cpp
index d1638d9..a4d482e 100644
--- a/src/security/v2/certificate-storage.cpp
+++ b/src/security/v2/certificate-storage.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,8 +26,8 @@
 namespace v2 {
 
 CertificateStorage::CertificateStorage()
-  : m_verifiedCertCache(time::hours(1))
-  , m_unverifiedCertCache(time::minutes(5))
+  : m_verifiedCertCache(1_h)
+  , m_unverifiedCertCache(5_min)
 {
 }
 
diff --git a/src/security/v2/key-chain.cpp b/src/security/v2/key-chain.cpp
index 9f496a1..348f214 100644
--- a/src/security/v2/key-chain.cpp
+++ b/src/security/v2/key-chain.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -549,7 +549,7 @@
 
   // set metainfo
   certificate.setContentType(tlv::ContentType_Key);
-  certificate.setFreshnessPeriod(time::hours(1));
+  certificate.setFreshnessPeriod(1_h);
 
   // set content
   certificate.setContent(key.getPublicKey().data(), key.getPublicKey().size());
@@ -559,7 +559,7 @@
   // Note time::system_clock::max() or other NotAfter date results in incorrect encoded value
   // because of overflow during conversion to boost::posix_time::ptime (bug #3915).
   signatureInfo.setValidityPeriod(ValidityPeriod(time::system_clock::TimePoint(),
-                                                 time::system_clock::now() + time::days(20 * 365)));
+                                                 time::system_clock::now() + 20 * 365_days));
 
   sign(certificate, SigningInfo(key).setSignatureInfo(signatureInfo));
 
diff --git a/src/security/v2/validation-policy-command-interest.hpp b/src/security/v2/validation-policy-command-interest.hpp
index 96a9012..84a7be8 100644
--- a/src/security/v2/validation-policy-command-interest.hpp
+++ b/src/security/v2/validation-policy-command-interest.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2017 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -62,7 +62,7 @@
      *  Setting this option to 0 or negative causes the validator to require exactly same
      *  timestamp as the system clock, which most likely rejects all command Interests.
      */
-    time::nanoseconds gracePeriod = time::seconds(120);
+    time::nanoseconds gracePeriod = 2_min;
 
     /** \brief max number of distinct public keys of which to record the last timestamp
      *
@@ -88,7 +88,7 @@
      *  Setting this option to 0 or negative makes last timestamp records expire immediately
      *  and causes every command Interest to be processed as initial.
      */
-    time::nanoseconds recordLifetime = time::hours(1);
+    time::nanoseconds recordLifetime = 1_h;
   };
 
   /** \brief constructor
@@ -157,5 +157,4 @@
 } // namespace security
 } // namespace ndn
 
-
 #endif // NDN_SECURITY_V2_VALIDATION_POLICY_COMMAND_INTEREST_HPP
diff --git a/src/security/v2/validation-policy-config.cpp b/src/security/v2/validation-policy-config.cpp
index c41a47f..0f0bb84 100644
--- a/src/security/v2/validation-policy-config.cpp
+++ b/src/security/v2/validation-policy-config.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -241,11 +241,11 @@
 
   switch (unit) {
     case 'h':
-      return time::duration_cast<time::nanoseconds>(time::hours(refreshPeriod));
+      return time::hours(refreshPeriod);
     case 'm':
-      return time::duration_cast<time::nanoseconds>(time::minutes(refreshPeriod));
+      return time::minutes(refreshPeriod);
     case 's':
-      return time::duration_cast<time::nanoseconds>(time::seconds(refreshPeriod));
+      return time::seconds(refreshPeriod);
     default:
       BOOST_THROW_EXCEPTION(Error(std::string("Wrong time unit: ") + unit));
   }
@@ -254,7 +254,7 @@
 time::nanoseconds
 ValidationPolicyConfig::getDefaultRefreshPeriod()
 {
-  return time::duration_cast<time::nanoseconds>(time::seconds(3600));
+  return 1_h;
 }
 
 void