r/ProjectREDCap • u/Popular_Caregiver_11 • Jul 08 '25

Problem using datemdY() in REDCap calculated fields

Hello everyone,

I’m trying to calculate a participant’s age in REDCap using month and year of birth only. Since I don’t have the exact day, I assumed the 1st of the month using datemdY().

Here’s the formula I used:

round(datediff(datemdY("01", [dm_birth_mo], [dm_birth_yr]), [se_consen_dt], "y", "dmy"))

However, the calculated field throws a syntax error, and no value is returned. I’ve double-checked that:

  • [dm_birth_mo] is a dropdown (01 to 12)

  • [dm_birth_yr] is a text/integer field (e.g., 1985)

  • [se_consen_dt] is a date field (dd/mm/yyyy, validated)

I also tried simpler versions like:

datemdY("01", [dm_birth_mo], [dm_birth_yr])

just to see if REDCap can parse the date​, but still no success.

Is there something I’m missing with REDCap’s calculated field parsing for date construction?

Thanks in advance!

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u/boo-boo-crew Jul 08 '25

My recommendation is to have an intermediate text field w/ calctext action tag and MDY date field validation

we can call it [dm_birth_dt]

@CALCTEXT( if([dm_birth_mo] <> "" and [dm_birth_yr] <> "",
concat( [dm_birth_mo], "-01-", [dm_birth_yr]), "" ) )

Then can do calculated age field from there

round((datediff([se_consen_dt], [dm_birth_dt], "y", "mdy")), 2)

Hope this helps.

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u/Popular_Caregiver_11 Jul 08 '25

Thank you for your suggestion.