security: Temporarily move the Time definition into common.hpp.
diff --git a/include/ndn-cpp/common.hpp b/include/ndn-cpp/common.hpp
index e9d0c88..a4ced37 100644
--- a/include/ndn-cpp/common.hpp
+++ b/include/ndn-cpp/common.hpp
@@ -53,6 +53,9 @@
namespace ndn {
+// TODO: Implement Time, used in certificates and DER encoding.
+typedef double Time;
+
/**
* Return the hex representation of the bytes in array.
* @param array The array of bytes.
diff --git a/include/ndn-cpp/security/identity/identity-manager.hpp b/include/ndn-cpp/security/identity/identity-manager.hpp
index 9028065..d31e214 100644
--- a/include/ndn-cpp/security/identity/identity-manager.hpp
+++ b/include/ndn-cpp/security/identity/identity-manager.hpp
@@ -16,9 +16,6 @@
namespace ndn {
-// TODO: Implement Time values.
-class Time;
-
/**
* An IdentityManager is the interface of operations related to identity, keys, and certificates.
*/
diff --git a/ndn-cpp/encoding/der/der.hpp b/ndn-cpp/encoding/der/der.hpp
index 82089d6..d85aa6e 100644
--- a/ndn-cpp/encoding/der/der.hpp
+++ b/ndn-cpp/encoding/der/der.hpp
@@ -25,9 +25,6 @@
namespace ndn {
-// TODO: Implement Time values.
-class Time;
-
namespace der {
enum DerType {