# Reindexing with date format conversion applied on dynamic fields matching regex
**URL:** https://discuss.elastic.co/t/reindexing-with-date-format-conversion-applied-on-dynamic-fields-matching-regex/237793
**Category:** Elasticsearch
**Created:** [June 19, 2020, 11:07am UTC](https://discuss.elastic.co/t/reindexing-with-date-format-conversion-applied-on-dynamic-fields-matching-regex/237793 "2020-06-19T11:07:49Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Andrei\_Gog](https://discuss.elastic.co/u/Andrei_Gog)
#### Post date: [June 19, 2020, 11:07am UTC](https://discuss.elastic.co/t/reindexing-with-date-format-conversion-applied-on-dynamic-fields-matching-regex/237793/1 "2020-06-19T11:07:49Z")
Hello Guys.
I have an index A that has fields **dt\_0** to **dt\_n** (n\<=100) that unfortunately are stored as dynamic mappings and represent the Long value of a date. The index B has the same mappings as A but it also has the right mapping for the **dt\_n** fields as shown below.
```auto
"dt_1": {
"type": "date",
"format": "strict_date_time"
}
```
Do you see any way I could use the reindex API to reindex from A to B and convert to date time only those fields that are name **dt\_** \*?
Here are the failures I get when I try to perform a basic reindex operation.
```auto
{
"took": 17151,
"timed_out": false,
"total": 459696,
"updated": 104999,
"created": 18000,
"deleted": 0,
"batches": 123,
"version_conflicts": 0,
"noops": 0,
"retries": {
"bulk": 0,
"search": 0
},
"throttled_millis": 0,
"requests_per_second": -1,
"throttled_until_millis": 0,
"failures": [
{
"index": "lc-uat-de1_accessgrant_project_v2",
"type": "accessible",
"id": "5eea03cec4839733aa11da6e",
"cause": {
"type": "mapper_parsing_exception",
"reason": "failed to parse [dt_1]",
"caused_by": {
"type": "illegal_argument_exception",
"reason": "Invalid format: \"1579478400000\" is malformed at \"478400000\""
}
},
"status": 400
}
]
}
```
Thank you!
---
### Author:  [@Vinayak\_Sapre](https://discuss.elastic.co/u/Vinayak_Sapre)
#### Post date: [June 19, 2020, 11:53pm UTC](https://discuss.elastic.co/t/reindexing-with-date-format-conversion-applied-on-dynamic-fields-matching-regex/237793/2 "2020-06-19T23:53:46Z")
Hi @Andrei_Gog
You can try using script in reindex. Assuming all values in dt\_1 in index A are epoch millis.
```auto
{
"source": {
"index": "A"
},
"dest": {
"index": "B"
},
"script": {
"source": "long milliSinceEpoch = ctx._source.remove(\"dt_1\"); Instant instant = Instant.ofEpochMilli(milliSinceEpoch); ZonedDateTime zdt = ZonedDateTime.ofInstant(instant, ZoneId.of('Z')); ctx._source.dt_1 = zdt;"
}
}
```
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 17, 2020, 11:53pm UTC](https://discuss.elastic.co/t/reindexing-with-date-format-conversion-applied-on-dynamic-fields-matching-regex/237793/3 "2020-07-17T23:53:47Z")
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