Removal of @timestamp field

I have added custom field eventLogTime which shows the time of logs generated. At the same time I want to remove @timestamp field.
However I am getting error when I tyr to remove @timestamp in logstash filter.

LogStash::Error: Unable to format in string "YYYY.MM.dd", @timestamp field not found

Please help me in this...!


I'm not sure removal of the @timestamp field is supported.