gistfile1.sh

DATE="$1"
yymmdd() {
  date -d"$DATE" '+%Y%m%d'
};

cat <<EOF | sed 's/^ *//'
  BEGIN:VCALENDAR
  VERSION:2.0
  PRODID:-//Hack and Tell//NONSGML v1.0//EN
  BEGIN:VEVENT
  UID: $(date +%s%N)@sg.hackandtell.org
  SUMMARY: Hack and Tell
  LOCATION: Hackerspace.SG, 344B King George's Avenue
  DESCRIPTION: Show and tell for hackers. Five minute demos, each followed by five minutes of questions.
  DTSTART;TZID=Asia/Singapore: $(yymmdd)T200000
  DTEND;TZID=Asia/Singapore: $(yymmdd)T220000
  END:VEVENT
  END:VCALENDAR
EOF

% curl -s https://gist.github.com/fmap/8294538/raw/a27c9e76cffd26d6e03618100551197a008e40e3/gistfile1.sh | sh -s '20140128' > ht.ics
% ./icaltest ht.ics
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Hack and Tell//NONSGML v1.0//EN
BEGIN:VEVENT
UID: 1389074470032262971
SUMMARY: Hack and Tell
LOCATION: Hackerspace.SG, 344B King George's Avenue
DESCRIPTION: Show and tell for hackers. Five minute demos, each followed
 by five minutes of questions.
DTSTART;TZID=Asia/Singapore: 20140128T200000
DTEND;TZID=Asia/Singapore: 20140128T220000
END:VEVENT
END:VCALENDAR
% echo $?
0