How do I do date math in a bash script on OS X Leopard?

Question

I realize I could whip up a little C or Ruby program to do this, but I want my script to have as few dependencies as possible.

Given that caveat, how does one d

Answer 1

Here is a script that I use to print the dates for my journal in google doc's:

    #!/bin/bash

    # ask user for variable details
    read -p 'Starting date in "mm-dd-yyyy" format: ' DATE

    # adjust the count by editing the "x" number in {0..x}
    # 91 days will give you about 3 months, currently set to 6 for testing
    # %a gives short day of the week, -m -d gives single digit months and days, capital Y gives 4 digit year

    for i in {0..6}
    do
         NEXT_DATE=$(date -j -f %m-%d-%Y -v+"$i"d $DATE +'%a %-m/%-d/%y')
         echo -e "$NEXT_DATE\n\n\n"
    done

Here is the sample output, (I use 3 new lines between each date):

Sun 4/1/18

Mon 4/2/18

Tue 4/3/18

Wed 4/4/18

Thu 4/5/18

Fri 4/6/18

Sat 4/7/18