A date that looks wrong may have the correct stored day but an unfamiliar display order. It may also have been interpreted as the wrong day during entry. These problems need different repairs.
Separate appearance from interpretation
Inspect the spreadsheet’s locale under File > Settings. Then examine a date whose day exceeds twelve, alongside ambiguous values such as 03/04. This helps reveal whether the source convention was month/day or day/month.
Apply a clear custom date format to a sample. If the resulting calendar date is correct, changing the display may be sufficient. If the stored date is wrong, a new display format will faithfully show the wrong date in another style.
Use an explicit date when repairing data
For a known date, =DATE(2026,4,3) constructs April 3, 2026 without relying on the order of a slash-separated string. Use the source’s actual year, month, and day rather than assuming every ambiguous entry follows the same convention.
Test repairs in helper columns. Retain the original imported text, especially when multiple regions supplied records. Formatting alone should not be described as automatically reinterpreting every existing cell.
Review the whole-file effect
Locale changes affect default date, number, and currency formatting for the spreadsheet and its collaborators. Coordinate the change instead of treating it as a private display preference.
Check date sorting, month totals, and exported samples after the repair. Include dates near month and year boundaries. If the source does not establish which interpretation was intended, flag those records for review rather than converting an uncertain date into an apparently authoritative one.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.