Subtract Days from a Date in Bash

subtract days from a date in bash

You are specifying the date incorrectly. Instead, say:

date --date="${dataset_date} -${date_diff} day" +%Y-%m-%d

If you need to store it in a variable, use $(...):

p_dataset_date=$(date --date="${dataset_date} -${date_diff} day" +%Y-%m-%d)

How to subtract or add date from a variable?

With GNU date it can be done quite easily with its -d switch.

x=20170402
date -d "$x -1 days" "+%Y%m%d"
20170401

and for 2 days

date -d "$x - 2 days" "+%Y%m%d"
20170331

How subtract days from date in bash shell on Solaris 11?

If you don't have GNU date or GNU awk, consider perl:

subtractDays() {
  local date numDays
  date=$1
  numDays=$2

  date=$date days=$numDays perl -e '
    use Env qw(date days);
    use Time::Piece;
    use Time::Seconds;

    my $start_time = Time::Piece->strptime($date, "%Y-%m-%d");
    my $end_time = $start_time - (ONE_DAY * $days);
    print $end_time->ymd . "\n";'
}

...thereafter:

subtractDays 2000-12-31 1

...emits...

2000-12-30

Today's date, minus X days in shell script

For GNU date:

date_222days_before_TodayYear=$(date --date="222 days ago" +"%Y")
date_222days_before_TodayMonth=$(date --date="222 days ago" +"%m")
date_222days_before_TodayDay=$(date --date="222 days ago" +"%d")

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For BSD date::

If you are using OS X or FreeBSD, use the following instead because BSD date is different from GNU date:

date_222days_before_TodayYear=$(date -j -v-222d +"%Y")
date_222days_before_TodayMonth=$(date -j -v-222d +"%m")
date_222days_before_TodayDay=$(date -j -v-222d +"%d")

Source: BSD date manual page

Note:

In bash and many other languages, you cannot start a variable name with a numerical character, so I prefixed them with date_ for you.

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Second Update: New requirement - Using 222 Working days instead of 222 Regular days:

(Assumption: Not considering statutory holidays, because that just gets far beyond the scope of what I can help you with in a shell script:)

Consider 222 working days:

• 5 working days per week, that is floor(222/5) == 44 weeks
• 44 weeks * 7 days per week == 308 days
• Extra days leftover: 222 % 5 == 2
• Therefore 222 working days == 310 regular days

But, there is a catch! If the number of regular days is 308 or some multiple of 7, then we would have been fine, because any multiple of 7-days ago from a working day is still a working day. So we need to consider whether today is a Monday or a Tuesday:

• If today is a Monday, we'd get Saturday where we wanted Thursday
• If today is a Tuesday, we'd get Sunday where we wanted Friday

So you see we need an additional offset of 2 more days if today is either Monday or Tuesday; so let's find that out first before we proceed:

#!/bin/bash

# Use 310 days as offset instead of 222
offset=310
# Find locale's abbreviated weekday name (e.g., Sun)
today=$(date -j +"%a")
# Check for Mon/Tue
if [[ "$today" == "Mon" ]] || [[ "$today" == "Tue" ]]; then
     offset=$((offset+2))
fi

date_222_working_days_before_TodayYear=$(date -j -v-${offset}d +"%Y")
date_222_working_days_before_TodayMonth=$(date -j -v-${offset}d +"%m")
date_222_working_days_before_TodayDay=$(date -j -v-${offset}d +"%d")

And that should do it =)

Get the date (a day before current time) in Bash

Sorry not mentioning I on Solaris system.
As such, the -date switch is not available on Solaris bash.

I find out I can get the previous date with little trick on timezone.

DATE=`TZ=MYT+16 date +%Y-%m-%d_%r`
echo $DATE

Bash Shell Current Date Minus Number of Days

Try doing this :

#!/bin/sh
#
# BACKUP DB TO S3
#

# VARIABLES
TYPE="DATABASE"
DAYS="30"

# GET CURRENT DATETIME
CURRENTDATE="$(date +%Y%m%d%H%M%S)"

# GENERATE PAST DATE FROM DAYS CONSTANT
OLDERDATE="$(date "+%Y%m%d%H%M%S" -d "$DAYS days ago")"

# CALL PYTHON SCRIPT WITH OLDERDATE ARGUMENT
python script.py "$OLDERDATE"

See info coreutils 'date invocation' | less +/28.7\ Relative\ items\ in\ date\ strings

How to subtract today's date with a file's modification date in unix?

Use %s seconds since 1970-01-01 00:00:00 UTC as in

echo $(expr $(date +%s) - $(date -r sample.txt +%s)) #!/bin/sh
echo $(($(date +%s) - $(date -r sample.txt +%s))) #/bin/bash

How to subtract two different date formats to get days in bash?

Try this:

let diff=(`date +%s -d 11/2/2015` - `date +%s`)/86400
echo $diff days remaining

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