Bash script: Checking today's date against a date without year - bash

Question

I'd like to send a renewal reminder email out four weeks before an expiry date. I'm storing all the details in an array, but I can't figure out how I check if today's date is 28 days before the date in the array.
Here's what I've got so far, any help with how to do the date checking would be much appreciated:
#!/bin/sh
adminemail="me#gmail.com"
account[1]="June 03|john#gmail.com|John"
account[2]="April 17|jane#gmail.com|Jane"
account[3]="November 29|sarah#gmail.com|Sarah"
for check in "${account[#]}"
do
renew=$(echo $check | cut -f1 -d\|)
email=$(echo $check | cut -f2 -d\|)
name=$(echo $check | cut -f3 -d\|)
# check date is 28 days away
if [ ?????? ]
then
subject="Your account is due for renewal"
text="
Dear $name,
Your account is due for renewal by $renew. blah blah blah"
echo "$text" | mail -s "$subject" $email -- -r $adminemail
fi
done

Answer 1

You can get the month and date of 28 days before the check date like this:
warning_date=$(date --date='June 03 -28 days' +%s)
The current date in the same format:
current_date=$(date +%s)
Since they are both numeric and in the same scale (seconds since epoch), now you can check if $current_date is greater than $warning_date:
if [ $warning_date -lt $current_date ]; then
# ...
fi
Put it all together now:
# ...
current_date=$(date +%s)
for check in ${account[#]}; do
# ...
renew=$(echo $check | cut -f1 -d\|)
# 28 days before the account renewal date
warning_date=$(date --date="$renew -28 days" +%m%d)
if [ $warning_date -lt $current_date ]; then
# Set up your email and send it.
fi
done
Update
To be reminded only if current date is the 28th day prior to the check date you can get each date in the same month date format and compare for string equality:
# ...
current_date=$(date "+%B %d")
for check in ${account[#]}; do
# ...
renew=$(echo $check | cut -f1 -d\|)
# The 28th day before the account renewal day
warning_date=$(date --date="$renew -28 days" "%B %d")
if [ $warning_date == $current_date ]; then
# Set up your email and send it.
fi
done

Answer 2

It's best to use Unix timestamps for date comparisons, as they are simple integers.
#!/bin/bash
adminemail="me#gmail.com"
account[1]="June 03|john#gmail.com|John"
account[2]="April 17|jane#gmail.com|Jane"
account[3]="November 29|sarah#gmail.com|Sarah"
for check in "${account[#]}"
do
IFS="|" read renew email name <<< "$check"
# GNU date assumed. Similar commands are available for BSD date
ts=$( date +%s --date "$renew" )
now=$( date +%s )
(( ts < now )) && (( ts+=365*24*3600 )) # Check the upcoming date, not the previous
TMINUS_28_days=$(( ts - 28*24*3600 ))
TMINUS_29_days=$(( ts - 29*24*3600 ))
if (( TMINUS_29_days < now && now < TMINUS_28_days)); then
subject="Your account is due for renewal"
mail -s "$subject" "$email" -- -r "$adminemail" <<EOF
Dear $name,
Your account is due for renewal by $renew. blah blah blah
EOF
fi
done