I have the same issue as [Still Not Solved!] Filebeat cannot recognize timezone in syslog
HAProxy logs have the correct date on the server, the server timezone is set to UTC-8 (Pacific), but the timestamp being sent to elasticsearch doesn't have the timezone info.
e.g this log file entry was generated at 9:39am PDT
"@timestamp": "2019-08-22T09:39:29.445Z",