This is a quick Linux shell script which, when bound to a keyboard shortcut, allows you to highlight a Unix timestamp (seconds, milliseconds, microseconds, hex) or a MongoDB ObjectID [double clicking to highlight/select works great here], mash your keyboard shortcut and see a popup of the date/time in your specified format. It also copies it to …

timestamp2date.sh

#!/bin/bash

DATE_FORMAT="%F %T %Z"
SEL=$(xclip -o | sed 's/[^0-9A-Fa-f]//g')

notify () {
    # hack to allow more than one alert to be sent every 6 seconds
    pkill -9 -f "notify-osd"
    notify-send -i appointment-new "$1"
}

datetime () {
    echo -n "$(date -d@"${1}" +"${DATE_FORMAT}")"
}

is_digits=$(echo "${SEL}" | grep -Eq "^[0-9]+$" >/dev/null 2>&1; echo -n $?)
is_hex=$(echo "${SEL}" | grep -Eq "^[0-9A-Fa-f]+$" >/dev/null 2>&1; echo -n $?)

if [[ $is_digits == 0 && ( ${#SEL} == 16 || ${#SEL} == 13 || ${#SEL} == 10 ) ]]; then
    # us, ms or seconds since epoch
    SEL="${SEL:0:10}"
    datetime "${SEL}" | xclip -sel clip
    notify "$(datetime "${SEL}")"
elif [[ $is_hex == 0 && ( ${#SEL} == 24 || ${#SEL} == 8 ) ]]; then
    # seconds since epoch in hex or full MongoDB ObjectID
    TS=$(echo "ibase=16; $(echo "${SEL:0:8}" | tr '[:lower:]' '[:upper:]')" | bc)
    datetime "${TS}" | xclip -sel clip
    notify "$(datetime "${TS}")"
else
    # fail
    pkill -9 -f "notify-osd"
    notify-send -i face-angry "not a valid timestamp"
fi