##*******************************************************************************
## Script       epoch
## Purpose      Take date in formatted string as an argument and coverts it
##              into epoch time (seconds since 1/1/1970)
## Usage        ./epoch Aug 25 23:59:59 2007 GMT
##===============================================================================
## History
## 2007/01/15  Big Kahoona   Creation of script (some code from the internet)
##*******************************************************************************

year=$4
month=$1
day=$2
hour=$(echo $3 | cut -d: -f1)
min=$(echo $3 | cut -d: -f2)
sec=$(echo $3 | cut -d: -f3)
tz=$5

# Convert month to number
if [ $month = "Jan" ]; then
        month=1
elif [ $month = "Feb" ]; then
        month=2
elif [ $month = "Mar" ]; then
        month=3
elif [ $month = "Apr" ]; then
        month=4
elif [ $month = "May" ]; then
        month=5
elif [ $month = "Jun" ]; then
        month=6
elif [ $month = "Jul" ]; then
        month=7
elif [ $month = "Aug" ]; then
        month=8
elif [ $month = "Sep" ]; then
        month=9
elif [ $month = "Oct" ]; then
        month=10
elif [ $month = "Nov" ]; then
        month=11
elif [ $month = "Dec" ]; then
        month=12
fi

# leap days in past years
leapdays=$(( (year - 1969)/4 ))

# Is this year a leap year?
leap=$(( year % 4 == 0 ))

# Days in each month this year.
mdays[1]=31
mdays[2]=$((28+leap))
mdays[3]=31
mdays[4]=30
mdays[5]=31
mdays[6]=30
mdays[7]=31
mdays[8]=31
mdays[9]=30
mdays[10]=31
mdays[11]=30
mdays[12]=31

# days since the epoch, not counting earlier months this year
daycount=$(( (year - 1970) * 365 + leapdays + day - 1))

# Step through earlier months this year and add the days
m=$((month - 1))
while [ $m -ge 1 ]; do
        #echo "month=$m"
        daycount=$((daycount+${mdays[$m]} ))
        m=$((m-1))
done

# Now the seconds
epoch=$(( ( (daycount * 24 + hour) * 60 + min) * 60 + sec ))

# Add the time zones that apply to you
case "$tz" in
        #GMT) epoch=$((epoch + 0));;
        #EST) epoch=$((epoch + 18000));;
        CST) epoch=$((epoch + 21600));;
        #GMT) epoch=$((epoch + 21600));;
        #*)   epoch="ERROR: unrecognized on time zone";;
esac
echo "${epoch}"