How to preserve timestamp while re-indexing?

I'm reindexing from 6.4 to 7.9 and while I got all documents as it is one thing I noticed timestamp is different, how do I preserve old timestamp in the document?

How did you reindex?

Hi dadoonet,

Thanks for the quick replay, here is how I'm reindexing it:

 curl -X POST "https://els02:9200/_reindex?pretty" -u admin:admin --insecure -H 'Content-Type: application/json' -d'
    {
      "source": {
        "remote": {
          "host": "http://elk01:9200"
        },
        "index": "logstash-2020.10.07"
      },
      "dest": {
        "index": "logstash-2020.10.07"
      }
    }
    '

Do you have an example of a document from the source which has a different content in the destination? Could you share both?

dadoonet I'm sorry for the trouble I misread it, this is embarrassing :man_facepalming:
the timestamp is preserved.