# Capturing Date on a File Once a Year

**URL:** <https://forums.knack.com/t/capturing-date-on-a-file-once-a-year/14702>\
**Category:** Get Answers\
**Created:** [August 5, 2023, 4:15pm UTC](https://forums.knack.com/t/capturing-date-on-a-file-once-a-year/14702 "2023-08-05T16:15:50Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Stephanie2](https://avatars.discourse-cdn.com/v4/letter/s/e8c25b/32.png) [@Stephanie2](https://forums.knack.com/u/Stephanie2)\
**Post date:** [August 5, 2023, 4:15pm UTC](https://forums.knack.com/t/capturing-date-on-a-file-once-a-year/14702/1 "2023-08-05T16:15:50Z")

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I’m working with three tables in my Knack app: ‘Participant,’ ‘Center,’ and ‘Center Attendance.’ Each participant can attend multiple centers, and I want to track their attendance dates. I need help with a formula to set a date field in the ‘Center Attendance’ table. Specifically, I want the formula to do the following:

1. If a participant attends a center after July 1st, I want to record their attendance date.
2. However, I only want to record the attendance date the first time they attend that specific center.

Can someone guide me on how to create a formula for this scenario? I’m using the ‘Participant’ table, the ‘Center’ table (with center names like Burlington, Norfolk, etc.), and the ‘Center Attendance’ table (with an ‘Attendance Date’ field). I appreciate any help or examples you can provide!

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**Author:** ![Laurent](https://sea2.discourse-cdn.com/flex020/user_avatar/forums.knack.com/laurent/32/2855_2.png) [@Laurent](https://forums.knack.com/u/Laurent)\
**Post date:** [August 9, 2023, 4:35pm UTC](https://forums.knack.com/t/capturing-date-on-a-file-once-a-year/14702/2 "2023-08-09T16:35:09Z")

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Hm, that depends if how you set it up precisely (for instance if “Center attendance” is a child of “Center”, and how many centers you have), but I would go with:

For each participant, add a field for each Center:  
COUNT-MIN (date) of [Center Attendance-\>Date fields], where the Center is the one you want.

I don’t know easy ways to take MINs of dates, but I usually converts dates into number of days and take the min of that.

Hope it is somewhat clear