Convert Date Formats in CSV Files

Last updated: March 2026 • 5 min read

"03/04/2026" — is that March 4th or April 3rd? Date format inconsistency is one of the most common CSV problems. Here's how to fix it.

Common Date Formats

Python Solution

import pandas as pd

df = pd.read_csv('data.csv')

# Parse ambiguous dates (dayfirst=True for EU format)
df['date'] = pd.to_datetime(df['date'], dayfirst=True)

# Convert to ISO format
df['date'] = df['date'].dt.strftime('%Y-%m-%d')

df.to_csv('data_fixed.csv', index=False)

Excel Formula

=TEXT(A1,"YYYY-MM-DD")