[BUG] Date Processor can't map @timestamp correctly

[powerpower2005]

Describe the bug

I'm trying to use opensearch ingestion and data prepper for logging and visualized with opensearch

Log has a field time with format like "yy/MM/dd HH:mm:ss.SSS"
EX) 24/10/28 13:35:45.721

I want to make this to timstamp, so I use date processor like below

- date:
      match:
        - key: time
          patterns: ["yy/MM/dd HH:mm:ss.SSS"]
      destination: "@timestamp"

expect result
time and @timestamp are same value.

result
but @timestamp has been disappeared.

As I know timezone is optional and rather default value is system time zone. So I search the log within 3 days. It doesn't work
But this log doesn't have a field @timestamp anymore. and I can't see any histgram on dashboard.
So I try it with another method

I set the timezone source and destination.

- date:
      match:
        - key: time
          patterns: ["yy/MM/dd HH:mm:ss.SSS"]
      destination: "@timestamp"
      source_timezone: "Asia/Seoul"
      destination_timezone: "Asia/Seoul"

Finally, It works.

But I wonder why it happen.

I always appreciate your work.

Related component
Plugins

To Reproduce

use any date type field to @timestamp without setting timezone.
In that case, you'll never get any logs on dashboard.

Expected behavior

Expect
time : 24/10/28 21:23:25.083
-> @timestamp : 2024/10/28 21:23:25.083

Additional Details
Plugins
Data Prepper

Environment

Opensearch 2.11
fluent-bit 3.11 ( Log Source throught HTTP)

[powerpower2005]

I think there is some problem with putting timestamp on a record.

DateProcessor.java line104

I think Timezone is optionally value. Even though zonedDateTime is null, we still need to put timestamp on a record.

I'm not good at java. if some logical error.

please forgive me generously.

[powerpower2005]

If you think it is a bug and you didn't start yet, Can I fix it?