Script to convert the date format in a CSV from an arbitrary format to ISO 8601

fix_date_format.py

import sys
import csv
from datetime import datetime

# Replaces a CSV column reformatting the date according to ISO 8601 standard with millis
# Usage: python fix_date_format.py < input.csv > output.csv

COLUMN_TO_REFORMAT_INDEX = 0
INPUT_FORMAT = '%d.%m.%Y, %H:%M:%S.%f'

def reformat_date(date_str):
    # Parse the date and time from the input format
    date_time_obj = datetime.strptime(date_str, '%d.%m.%Y, %H:%M:%S.%f')
    # Format the date and time to the desired output format
    return date_time_obj.strftime('%Y-%m-%d-T%H:%M:%S.%f')[:-3]

reader = csv.reader(sys.stdin)
writer = csv.writer(sys.stdout)

# Skip the first row (header)
header = next(reader)
writer.writerow(header)

# convert first column
for row in reader:
    if row:
        row[COLUMN_TO_REFORMAT_INDEX] = reformat_date(row[COLUMN_TO_REFORMAT_INDEX])
    writer.writerow(row)