Very quick and dirty bash script to do something I need on a regular basis - outputing a sequence of days between an (inclusive) start date and an (exclusive) end date.

days.sh

#!/bin/bash
if (( $# < 2 )); then
    echo "Usage:"
    echo
    echo "$0 1983-02-20 1983-03-13 [OUTPUT FORMAT] [--inclusive-end]"
    echo "Generates sequential dates in the specified format between the start and end dates provided."
    echo
    echo "$0 1983-02-20 20 [OUTPUT FORMAT] [--inclusive-end]"
    echo "Generates sequential dates in the specified format starting at the start date and continuing for the specified number of days."
    echo
    echo "In both modes of operation the generated dates are inclusive of the start date and exclusive of the end date, unless --inclusive-end is specified."
    exit 1
fi

function format_date() {
    local START=$1
    local X=$2
    local FORMAT=$3
    if [[ $(uname -s) = "Darwin" ]]; then
        echo `date -j -v +${X}d -f "%Y-%m-%d" ${START} +${FORMAT}`
    else
        echo `date -d "${START} ${X} days" +${FORMAT}`
    fi
}

function days_between() {
    local START=`format_date $1 0 +%s`
    local END=`format_date $2 0 +%s`
    local DAYS_BETWEEN=$((( $END - $START) / (60*60*24)))
    echo $DAYS_BETWEEN
}

START=$1
if echo $2 | egrep -q '^[0-9]+$'; then
    DAYS=$2
else
    DAYS=`days_between $START $2`
fi

shift
shift

INCLUSIVE_END=0
if [[ "$1" = "--inclusive-end" ]]; then
    INCLUSIVE_END=1
    shift
elif [[ "$2" = "--inclusive-end" ]]; then
    INCLUSIVE_END=1
fi

FORMAT=${1:-%Y-%m-%d}

for (( i = 0; i < $DAYS + $INCLUSIVE_END; i++ )); do
    echo `format_date $START $i $FORMAT`
done