# Calculation field for time between

**URL:** <https://community.hubspot.com/t/calculation-field-for-time-between/98995>\
**Category:** CRM\
**Tags:** crm\
**Created:** [January 30, 2024, 2:43pm UTC](https://community.hubspot.com/t/calculation-field-for-time-between/98995 "2024-01-30T14:43:56Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![CClark3](https://avatars.discourse-cdn.com/v4/letter/c/87869e/32.png) [@CClark3](https://community.hubspot.com/u/CClark3)\
**Post date:** [January 30, 2024, 2:43pm UTC](https://community.hubspot.com/t/calculation-field-for-time-between/98995/1 "2024-01-30T14:43:56Z")

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I have a bit of dilemna and was hoping it could be solved by a workflow or custom formula( the ones I’ve tried seem to not work). I’m trying to add a duration field ( In months example: 6 months) to a start date field which is in date format( 2/1/2024). IN the calculated property i created I used this formula: [properties.expected\_project\_start\_date]+ ([properties.duration]/12\*365) = End date(In date format)

however I just get the project start date and not getting the desired date. Any help would be appreciated if this is even possible

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**Author:** ![karstenkoehler](https://d10pqhm3lwygmk.cloudfront.net/user_avatar/community.hubspot.com/karstenkoehler/32/68554_2.png) [@karstenkoehler](https://community.hubspot.com/u/karstenkoehler)\
**Post date:** [January 30, 2024, 2:46pm UTC](https://community.hubspot.com/t/calculation-field-for-time-between/98995/2 "2024-01-30T14:46:59Z")

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Hi @CClark3,

HubSpot measures time in milliseconds, not days - can you try adjusting your formula accordingly?

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**Author:** ![Lucila-Andimol](https://d10pqhm3lwygmk.cloudfront.net/user_avatar/community.hubspot.com/lucila-andimol/32/69276_2.png) [@Lucila-Andimol](https://community.hubspot.com/u/Lucila-Andimol)\
**Post date:** [January 30, 2024, 7:09pm UTC](https://community.hubspot.com/t/calculation-field-for-time-between/98995/3 "2024-01-30T19:09:40Z")

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Hey @CClark3

in this article you can have some more insight about how to [Calculate values based on time between two properties.](https://knowledge.hubspot.com/properties/create-calculation-properties)

You can see the explanations about milliseconds that Karsten Mentioned.

hope this helps