# Question Regarding Data Calculations

**URL:** <https://forum.dimagi.com/t/question-regarding-data-calculations/9480>\
**Category:** Users\
**Created:** [November 28, 2022, 1:49am UTC](https://forum.dimagi.com/t/question-regarding-data-calculations/9480 "2022-11-28T01:49:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![JZUser95](https://dimagi.b-cdn.net/letter_avatar_proxy/v4/letter/j/71c47a/32.png) [@JZUser95](https://forum.dimagi.com/u/JZUser95)\
**Post date:** [November 28, 2022, 1:49am UTC](https://forum.dimagi.com/t/question-regarding-data-calculations/9480/1 "2022-11-28T01:49:10Z")

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Hi! Are date calculations static, or do they change based of off the system date and time? For example, if you include a calculated value age variable in a survey that is the calculation of a subject's age (difference between today's date and subject's date of birth), does the calculated age variable update or change with time, does it stay the same?

Any input regarding this would be much appreciated; thanks!

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**Author:** ![Ethan\_Soergel](https://dimagi.b-cdn.net/user_avatar/forum.dimagi.com/ethan_soergel/32/543_2.png) [@Ethan\_Soergel](https://forum.dimagi.com/u/Ethan_Soergel)\
**Post date:** [November 28, 2022, 3:12pm UTC](https://forum.dimagi.com/t/question-regarding-data-calculations/9480/2 "2022-11-28T15:12:12Z")

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They are static - the expression is calculated when the form is filled out, and only the result is saved to the case. For things like age, it's probably most appropriate to store the date of birth and calculate the current age as needed.