diff --git a/src/security/validity-period.hpp b/src/security/validity-period.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2015 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_SECURITY_VALIDITY_PERIOD_HPP
+#define NDN_SECURITY_VALIDITY_PERIOD_HPP
+
+#include "../common.hpp"
+#include "../encoding/tlv.hpp"
+#include "../encoding/block.hpp"
+#include "../util/time.hpp"
+
+namespace ndn {
+namespace security {
+
+
+/** @brief Abstraction of validity period
+ *  @sa docs/tutorials/certificate-format.rst
+ */
+class ValidityPeriod
+{
+public:
+  class Error : public tlv::Error
+  {
+  public:
+    explicit
+    Error(const std::string& what)
+      : tlv::Error(what)
+    {
+    }
+  };
+
+public:
+  /** @brief Set validity period (UNIX epoch, UNIX epoch) that is always invalid
+   */
+  ValidityPeriod() = default;
+
+  /** @brief Create validity period from @p block
+   */
+  explicit
+  ValidityPeriod(const Block& block);
+
+  /** @brief Create validity period (@p notBefore, @p notAfter)
+   *  @param notBefore exclusive beginning of the validity period range
+   *  @param notAfter exclusive end of the validity period range
+   *
+   *  @note The supplied time points will be rounded up to the whole seconds:
+   *        - @p notBefore is rounded up the next whole second
+   *        - @p notAfter is truncated to the previous whole second
+   */
+  ValidityPeriod(const time::system_clock::TimePoint& notBefore,
+                 const time::system_clock::TimePoint& notAfter);
+
+  /** @brief Check if @p now falls within the validity period
+   *  @param now Time point to check if it falls within the period
+   *  @return periodBegin < @p now and @p now < periodEnd
+   */
+  bool
+  isValid(const time::system_clock::TimePoint& now = time::system_clock::now()) const;
+
+  /** @brief Set validity period (@p notBefore, @p notAfter)
+   *  @param notBefore exclusive beginning of the validity period range
+   *  @param notAfter exclusive end of the validity period range
+   *
+   *  @note The supplied time points will be rounded up to the whole seconds:
+   *        - @p notBefore is rounded up the next whole second
+   *        - @p notAfter is truncated to the previous whole second
+   */
+  ValidityPeriod&
+  setPeriod(const time::system_clock::TimePoint& notBefore,
+            const time::system_clock::TimePoint& notAfter);
+
+  /** @brief Get the stored validity period
+   */
+  std::pair<time::system_clock::TimePoint, time::system_clock::TimePoint>
+  getPeriod() const;
+
+  /** @brief Fast encoding or block size estimation
+   */
+  template<encoding::Tag TAG>
+  size_t
+  wireEncode(EncodingImpl<TAG>& encoder) const;
+
+  /** @brief Encode ValidityPeriod into TLV block
+   */
+  const Block&
+  wireEncode() const;
+
+  /** @brief Decode ValidityPeriod from TLV block
+   *  @throw Error when an invalid TLV block supplied
+   */
+  void
+  wireDecode(const Block& wire);
+
+public: // EqualityComparable concept
+  bool
+  operator==(const ValidityPeriod& other) const;
+
+  bool
+  operator!=(const ValidityPeriod& other) const;
+
+private:
+  typedef boost::chrono::time_point<time::system_clock, time::seconds> TimePoint;
+
+  TimePoint m_notBefore;
+  TimePoint m_notAfter;
+
+  mutable Block m_wire;
+};
+
+std::ostream&
+operator<<(std::ostream& os, const ValidityPeriod& period);
+
+} // namespace security
+} // namespace ndn
+
+#endif // NDN_SECURITY_VALIDITY_PERIOD_HPP