# Substracting two datetime fields
**URL:** https://discuss.elastic.co/t/substracting-two-datetime-fields/135619
**Category:** Elasticsearch
**Created:** [June 13, 2018, 3:52am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619 "2018-06-13T03:52:30Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Illidan](https://discuss.elastic.co/u/Illidan)
#### Post date: [June 13, 2018, 3:52am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/1 "2018-06-13T03:52:30Z")
This is a field in my document:
"date\_found": "2018-04-23T22:17:46.6387919+03:00"
My goal is to calculate some value from difference between two datetime fields (e.g. dt1 - dt2)
I running a script to perform such operation:
updateDescriptor.Script(a =\> a.Inline("ctx.\_source.lifetime = ctx.\_source.date\_deleted - ctx.\_source.date\_found"));
This operation results with the following error:
"Cannot apply [-] operation to types [java.lang.String] and [java.lang.String]."
How it is advised to perform operations on datetime fields?
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### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [June 13, 2018, 4:21am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/2 "2018-06-13T04:21:52Z")
I don't remember by heart the syntax but I believe you need first to transform the date object to ms since epoch and then you can do a substraction.
Have a look at what are the available methods for a date type field.
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### Author:  [@Illidan](https://discuss.elastic.co/u/Illidan)
#### Post date: [June 13, 2018, 5:32am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/3 "2018-06-13T05:32:54Z")
Can I perform such conversion as part of script execution? Where I can find list of available methods you are mentioning?
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### Author:  [@roshni](https://discuss.elastic.co/u/roshni)
#### Post date: [June 13, 2018, 5:40am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/4 "2018-06-13T05:40:10Z")
You can refer to the below link -
[https://www.elastic.co/guide/en/elasticsearch/reference/6.1/mapping-date-format.html](https://www.elastic.co/guide/en/elasticsearch/reference/6.1/mapping-date-format.html)
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### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [June 13, 2018, 6:05am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/5 "2018-06-13T06:05:59Z")
On a mobile now but a quick search and I found
>
HTH
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### Author:  [@Illidan](https://discuss.elastic.co/u/Illidan)
#### Post date: [June 13, 2018, 6:20am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/6 "2018-06-13T06:20:22Z")
On mobile now but from quick view it looks like what I need.
Thanks man
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 11, 2018, 6:26am UTC](https://discuss.elastic.co/t/substracting-two-datetime-fields/135619/7 "2018-07-11T06:26:49Z")
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