days-left

.days

20170414120000 Revision 2017 (for Visitors)
20160701120000 Nordlicht 2016
20160812120000 Evoke 2016

days-left.sh

#!/bin/sh
# 3B8544DA-587F-4FA7-9AFC-CB96A2B8197B

currentTime="$(date +%s)"
currentMinTime="$((2**31-1))"
currentMinEvent=""

daysFile="${HOME}/.days"

while read time event; do
	eventTime="$(date -jf %Y%m%d%H%M%S "${time}"0000 +%s 2> /dev/null)"
	if [ "${eventTime}" -gt "${currentTime}" -a "${eventTime}" -lt "${currentMinTime}" ]; then
		if [[ -z "${1}" || ( -n "${1}" && "${event}" =~ "${1}" ) ]]; then
			currentMinTime="${eventTime}"
			currentMinEvent="${event}"
		fi
	fi
done < "${daysFile}"

if [ -z "${currentMinEvent}" ]; then
	exit
fi

daysLeft="$(((${currentMinTime} - ${currentTime})/86400))"
echo "${daysLeft} days left until ${currentMinEvent}."

Copy days-left.sh to somewhere in your PATH, copy .days to your $HOME, and start adding entries you need to be remembered about. Calling days-left.sh will then tell you how many days are left until the next event in your list (they are sorted in the script, no need to sort them in the file).

Tested on OS X only, GNU date might want different options.