title: log4j DailyRollingFileAppender does not create file with date pattern
body: <p>Using org.apache.log4j in a Java 8 application, I want a new log file to be created every hour with name e.g.: "mylog.log.2014-09-24-18". 
  I read I need to use DailyRollingFileAppender, but when I start the application the log file is named "mylog.log".</p>
  
  <p>This is the content of my log4j.properties file:</p>
  
  <pre><code># Set root logger level and its appenders
  log4j.rootLogger=DEBUG, file
  
  # Direct log messages to a log file
  log4j.appender.file=org.apache.log4j.DailyRollingFileAppender
  log4j.appender.file.DatePattern='.'yyyy-MM-dd-HH
  log4j.appender.file.Append=true
  log4j.appender.file.File=mylog.log
  log4j.appender.file.encoding=UTF-8
  log4j.appender.file.layout=org.apache.log4j.PatternLayout
  log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n
  </code></pre>
  
  <p>Can you please let me know how I can achieve this?</p>