title: Using log timestamp as @timestamp in elasticsearch
body: <p>I am trying to import jetty logs into elasticsearch via filebeat. </p>
  
  <p>the logs has the following format: </p>
  
  <pre><code>Sep 06, 2017 8:06:32 PM com.nphase.redcapcloud.server.managers.rules.RuleRunAsync executeSync
  INFO: Rule execution start: 3-6 Month Follow Up - Hide Imaging Form
  </code></pre>
  
  <p>logstash config looks like this:</p>
  
  <pre><code>filter {
    if "jetty" in [service] {
      grok {
        match =&gt; { "message" =&gt; ["%{MONTH:[system][jetty][month]} %{MONTHDAY:[system][jetty][day]}, %{YEAR:[system][jetty][year]} %{TIME:[system][jetty][time]}%{CRON_ACTION:[system][jetty][day_period]} %{NOTSPACE:[system][jetty][class]} %{WORD:[system][jetty][method]}\n%{GREEDYMULTILINE:[system][jetty][multiline]}"]}
        pattern_definitions =&gt; {
          "GREEDYMULTILINE" =&gt; "(.|\r|\n)*"
        }
     }
     mutate {
       add_field =&gt; {
         "timestamp_match" =&gt; "%{[system][jetty][month]} %{[system][jetty][day]}, %{[system][jetty][year]} %{[system][jetty][time]}%{[system][jetty][day_period]}"
       }
     }
     date {
       match =&gt; [ "timestamp_match",
                  "MM dd, YYYY KK:mm:ss aa",
                  "MM d, YYYY KK:mm:ss aa" ]
       timezone =&gt; "UTC"
     }
    }
  }
  </code></pre>
  
  <p>I have tried to match the date with the <code>timestamp_match</code> field but it is not working. Any idea of what can be wrong? </p>