A CSV that says 03/04/2026 means March 4 to HubSpot and 3 April to a European Salesforce org. Mixed date formats are the quiet reason imports "succeed" but your close dates, renewal dates, and last-contacted fields come out wrong or blank. These five Google Sheets fixes get every date into one safe format before you upload. Assume the raw date is in column D.
1. Find the dates that are really text
Sheets left-aligns text and right-aligns real dates. Flag the text ones:
=IF(ISNUMBER(D2),"date","TEXT - fix me") 2. Convert text dates to real dates
=IFERROR(DATEVALUE(TRIM(D2)),"") Blanks in the result are the rows a human needs to look at.
3. Fix day/month swaps from European exports
If the source was DD/MM/YYYY, rebuild it explicitly instead of trusting your locale:
=DATE(RIGHT(D2,4),MID(D2,4,2),LEFT(D2,2)) 4. Output ISO format for the importer
Most CRMs accept YYYY-MM-DD without guessing:
=TEXT(E2,"yyyy-mm-dd") 5. Catch impossible values
Close dates in 1900, birthdays in the future, last-contacted dates after today:
=IF(OR(E2<DATE(2000,1,1),E2>TODAY()+730),"CHECK","") Run all five on a copy, filter for "TEXT", blanks, and "CHECK", fix those by hand, then import only the ISO column.
Want the full pre-import pass (dedupe, phones, emails, names, dates, owner mapping)? The HubSpot/Salesforce Import Checklist ($9) walks through it step by step. Or get a CRM Hygiene Scorecard ($29) on your actual list: send a sample and you get back a scored report of what will break before you import.
