# Update format for an existing field of date type
**URL:** https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787
**Category:** Elasticsearch
**Created:** [September 3, 2019, 8:35am UTC](https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787 "2019-09-03T08:35:38Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Miao](https://discuss.elastic.co/u/Miao)
#### Post date: [September 3, 2019, 8:35am UTC](https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787/1 "2019-09-03T08:35:38Z")
I currently use ElasticSearch 7.2.0.
I followed the instructions [here](https://www.elastic.co/guide/en/elasticsearch/reference/7.x/mapping-date-format.html) to update the format of an existing field of date type:
```auto
{
"mappings": {
"properties": {
"TimeStamp": {
"type": "date",
"format": "yyyy-MM-ddTHH:mm:ssZ"
}
}
}
}
```
However, I received this error:
```auto
{
"error": {
"root_cause": [
{
"type": "resource_already_exists_exception",
"reason": "index [gaze/Po9kUGesSWCzfEME1sZ3Sg] already exists",
"index_uuid": "Po9kUGesSWCzfEME1sZ3Sg",
"index": "gaze"
}
],
"type": "resource_already_exists_exception",
"reason": "index [gaze/Po9kUGesSWCzfEME1sZ3Sg] already exists",
"index_uuid": "Po9kUGesSWCzfEME1sZ3Sg",
"index": "gaze"
},
"status": 400
}
```
Short of creating a new index with the desired mapping and then transferring all the data from the old index to the new one, how can I update the date format of an existing field?
---
### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [September 3, 2019, 8:50am UTC](https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787/2 "2019-09-03T08:50:02Z")
You can not update an existing field.
You can create a new field with the settings you want to use though.
If you need to update an existing field, you need to create a new index with the mapping you want to have and reindex all your data. The reindex API might help.
---
### Author:  [@Miao](https://discuss.elastic.co/u/Miao)
#### Post date: [September 3, 2019, 9:16am UTC](https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787/3 "2019-09-03T09:16:56Z")
Thanks for your reply. I tried re-indexing, but received many errors with similar messages:
```auto
{
"index": "gaze_new",
"type": "_doc",
"id": "fVj-8WwBPESVc1yT9rFL",
"cause": {
"type": "mapper_parsing_exception",
"reason": "failed to parse field [Timestamp] of type [date] in document with id 'fVj-8WwBPESVc1yT9rFL'",
"caused_by": {
"type": "illegal_argument_exception",
"reason": "failed to parse date field [2019-09-02T14:18:35.1714475 02:00] with format [yyyy-MM-dd'T'HH:mm:ssZ]",
"caused_by": {
"type": "date_time_parse_exception",
"reason": "Text '2019-09-02T14:18:35.1714475 02:00' could not be parsed at index 19"
}
}
},
"status": 400
}
```
Is this even possible to fix?
---
### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [September 3, 2019, 10:31am UTC](https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787/4 "2019-09-03T10:31:53Z")
You defined `yyyy-MM-dd'T'HH:mm:ssZ` as the format but you sent `2019-09-02T14:18:35.1714475 02:00` which has `.1714475` in addition.
I'm not expert in time format, but you need to find the right one [from this page](https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html) I guess. I'm not sure if we can parse nanoseconds with the standard date field type. You probably need to use [https://www.elastic.co/guide/en/elasticsearch/reference/current/date\_nanos.html](https://www.elastic.co/guide/en/elasticsearch/reference/current/date_nanos.html) in that case.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [October 1, 2019, 10:31am UTC](https://discuss.elastic.co/t/update-format-for-an-existing-field-of-date-type/197787/5 "2019-10-01T10:31:53Z")
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