Set the release date for 2.6.4.

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -2557,7 +2557,7 @@ Release 2.6.5 - UNRELEASED
     HADOOP-12589. Fix intermittent test failure of TestCopyPreserveFlag
     (iwasakims)
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES
 

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -3968,7 +3968,7 @@ Release 2.6.5 - UNRELEASED
     HDFS-9347. Invariant assumption in TestQuorumJournalManager.shutdown()
     is wrong. (Wei-Chiu Chuang via zhz)
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES
 

hadoop-mapreduce-project/CHANGES.txt

@@ -1044,7 +1044,7 @@ Release 2.6.5 - UNRELEASED
     MAPREDUCE-6191. Improve clearing stale state of Java serialization
                     testcase.  (Sam Liu via Eric Yang)
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES
 

hadoop-yarn-project/CHANGES.txt

@@ -2353,7 +2353,7 @@ Release 2.6.5 - UNRELEASED
 
   BUG FIXES
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES