# Expression Tag History Backfill

**URL:** <https://forum.inductiveautomation.com/t/expression-tag-history-backfill/39206>\
**Category:** Ignition\
**Created:** [September 29, 2020, 8:21pm UTC](https://forum.inductiveautomation.com/t/expression-tag-history-backfill/39206 "2020-09-29T20:21:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![bdavis](https://avatars.discourse-cdn.com/v4/letter/b/ce7236/32.png) [@bdavis](https://forum.inductiveautomation.com/u/bdavis)\
**Post date:** [September 29, 2020, 8:21pm UTC](https://forum.inductiveautomation.com/t/expression-tag-history-backfill/39206/1 "2020-09-29T20:21:32Z")

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I have created several simple expression tags that reference other tags within my UDT. The tags are calculating correctly and storing history moving forward, however I would like to have the expression calculate for the historical data as well. Is there a function to have this data backfill?

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [September 29, 2020, 8:23pm UTC](https://forum.inductiveautomation.com/t/expression-tag-history-backfill/39206/2 "2020-09-29T20:23:58Z")

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You’ll have to script the math, but you can backfill with [system.tag.storeTagHistory()](https://docs.inductiveautomation.com/display/DOC80/system.tag.storeTagHistory).