Stop Excel turning your data into dates.

What gets turned into a date

Excel's import recognises anything that could be read as a date in your region's settings:

With German settings the same happens to other shapes: a version number like 1.2 can become the first of February.

What it has cost

The gene names are the famous case. A 2016 study in Genome Biology found gene-name errors caused by spreadsheets in roughly one in five published papers that came with Excel gene lists. In 2020 the HUGO Gene Nomenclature Committee renamed the affected human genes — SEPT1 is now SEPTIN1, MARCH1 is MARCHF1 — partly so that spreadsheets would stop changing them. Outside science the same thing happens every day to sizes, ranges, version numbers and article codes, and nobody renames those.

How to prevent it in Excel

1. Import rather than open: Data ▸ From Text/CSV.
2. Set the affected columns to Text in the import preview before loading.
3. In recent versions of Microsoft 365, look at the settings for automatic data conversion, which let you switch off the conversion of letters and numbers into dates.

As with leading zeros, the conversion happens as the file opens — formatting the column afterwards cannot bring back SEPT1, because the cell now holds a date.

Keep every value as written

Intact CSV Editor never turns text into a date. 1/2 is 1/2, SEPT1 is SEPT1, and saving writes them back exactly. Where a column really does hold dates, the app still understands them: they sort as moments in time, filter with between and at least, and can be rewritten on purpose with Write the Dates Another Way — ISO 8601, day-first, US, Unix time or Excel serial numbers. Anything in the column that is not a date keeps its text.