# Copy \`@timestamp\` in Logstash
**URL:** https://discuss.elastic.co/t/copy-timestamp-in-logstash/139430
**Category:** Logstash
**Created:** [July 10, 2018, 9:14pm UTC](https://discuss.elastic.co/t/copy-timestamp-in-logstash/139430 "2018-07-10T21:14:22Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@amomchilov](https://discuss.elastic.co/u/amomchilov)
#### Post date: [July 10, 2018, 9:14pm UTC](https://discuss.elastic.co/t/copy-timestamp-in-logstash/139430/1 "2018-07-10T21:14:22Z")
I would like to preserve the `@timestamp` field prior to overwriting it from a `date` filter, so that I can know when a document was processed by logstash.
I also tried using the `copy` filter, but that fails silently.
```
mutate {
copy => { "%{@timestamp}" => "logstash_intake_timestamp" }
}
```
I tried this, but it also caused exceptions (I don't have the stack trace right now, but I could get it if it would help the investigation).
```
mutate {
copy => { "@timestamp" => "logstash_intake_timestamp" }
}
```
I tried using the `event` API, but it leads to [this exception](https://pastebin.com/ufdh2tx2).
```
ruby {
code => "event.set('read_time', event.get('@timestamp'))"
}
```
What's the correct way to copy `@timestamp`?
---
### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [July 11, 2018, 6:09am UTC](https://discuss.elastic.co/t/copy-timestamp-in-logstash/139430/2 "2018-07-11T06:09:36Z")
Might something like this work?
```auto
mutate {
add_field => { "logstash_intake_timestamp"=> "%{@timestamp}" }
}
```
---
### Author:  [@amomchilov](https://discuss.elastic.co/u/amomchilov)
#### Post date: [July 11, 2018, 6:25am UTC](https://discuss.elastic.co/t/copy-timestamp-in-logstash/139430/3 "2018-07-11T06:25:20Z")
Oh boy, I didn't RTFM:
> [@copy (emphasis mine)](#):
>
> Copy an existing field _ **to another field** _. Existing target field will be overriden.
> [@add\_field (emphasis mine)](#):
>
> If this filter is successful, add any arbitrary fields to this event. Field names can be dynamic and include parts of the event using the %{field}.
I'll try this tomorrow and report back!
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [August 8, 2018, 6:25am UTC](https://discuss.elastic.co/t/copy-timestamp-in-logstash/139430/4 "2018-08-08T06:25:28Z")
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