Removes all events preceeding a given year and month from an .ics calendar file.

trim-icalendar-ics

#!/bin/bash

# Usage: ./trim-icalendar-ics foo-bar.ics 2024 06
# Removes all events before 2024 and month May (or keeps everything from May 2024 onwards)
# and saves the remaining events into the file foo-bar.ics.out

# Note: current working directory must be the one where the ics file resides!

# Note for Mac and BSD users: this script requires the GNU version of csplit and sed!

# first argument - the calendar file.
# second argument - the year like 2024.
# third argument - the month as 01,02,03,...,09,10,11,12.

CALENDAR_FILE="$1"
YEAR="$2"
MONTH="$3"

temp_dir=temp
temp_files_digits=5

mkdir -p $temp_dir
cd $temp_dir

# split the calendar file into separate files for each event. This script creates multiple files in the form of xx00000
total_files=`csplit -n $temp_files_digits ../"$CALENDAR_FILE" '/BEGIN:VEVENT/' {*} | wc -l`

echo "total events found: " $total_files

# filters the split event files by year and month and reassembles the remaining ones into one file
grep -R DTSTART . \
    | sed -s "s/\.\/\(xx[0-9]\+\).*:\([0-9]\{4\}\)\([0-9]\{2\}\).*/\1 \2 \3/g" \
    | awk -v year="$YEAR" -v month="$MONTH" '{if($2>year || ($2==year && $3>=month)) print $1;}' \
    | xargs -L 1 cat > events

# creates the final shrunk ics file with the header and footer files
cat xx00000 events xx`printf "%05d" $((total_files-1))` > ../"$CALENDAR_FILE".out

cd ..
rm -r $temp_dir

Thanks for the new version of the script @ewaldbenes! However, there is a logical error in:

{if($2>=year && $3>=month) print $1;}

It filters out also the events from the further years, if a month is earlier. There should be something like:

{if($2>year || ($2==year && $3>=month)) print $1;}

Thanks for pointing out the error @szpak! I will correct the script.