csi_fix_ics.py

#!/usr/bin/env python3

import sys
import re

with open(sys.argv[1], "r", encoding="utf8") as fh:
    data = fh.read()
    
s = re.search(r"^(DTSTART:\d{8}T\d{6})$", data, re.MULTILINE).group(1)
data = data.replace(s, s+"Z")

s = re.search(r"^(DTEND:\d{8}T\d{6})$", data, re.MULTILINE).group(1)
data = data.replace(s, s+"Z")

with open(sys.argv[1], "w", encoding="utf8") as fh:
    fh.write(data)