How to format and manipulate dates ?

Format date

date +FORMAT

OR

date +"%FORMAT"

FORMATTING

%%

a literal %

%a

locale's abbreviated weekday name (e.g., Sun)

%A

locale's full weekday name (e.g., Sunday)

%b

locale's abbreviated month name (e.g., Jan)

%B

locale's full month name (e.g., January)

%c

locale's date and time (e.g., Thu Mar 3 23:05:25 2005)

%C

century; like %Y, except omit last two digits (e.g., 21)

%d

day of month (e.g, 01)

%D

date; same as %m/%d/%y

%e

day of month, space padded; same as %_d

%F

full date; same as %Y-%m-%d

%g

last two digits of year of ISO week number (see %G)

%G

year of ISO week number (see %V); normally useful only with %V

%h

same as %b

%H

hour (00..23)

%I

hour (01..12)

%j

day of year (001..366)

%k

hour ( 0..23)

%l

hour ( 1..12)

%m

month (01..12)

%M

minute (00..59)

%n

a newline

%N

nanoseconds (000000000..999999999)

%p

locale's equivalent of either AM or PM; blank if not known

%P

like %p, but lower case

%r

locale's 12-hour clock time (e.g., 11:11:04 PM)

%R

24-hour hour and minute; same as %H:%M

%s

seconds since 1970-01-01 00:00:00 UTC

%S

second (00..60)

%t

a tab

%T

time; same as %H:%M:%S

%u

day of week (1..7); 1 is Monday

%U

week number of year, with Sunday as first day of week (00..53)

%V

ISO week number, with Monday as first day of week (01..53)

%w

day of week (0..6); 0 is Sunday

%W

week number of year, with Monday as first day of week (00..53)

%x

locale's date representation (e.g., 12/31/99)

%X

locale's time representation (e.g., 23:13:48)

%y

last two digits of year (00..99)

%Y

year

%z

+hhmm numeric timezone (e.g., -0400)

%:z

+hh:mm numeric timezone (e.g., -04:00)

%::z

+hh:mm:ss numeric time zone (e.g., -04:00:00)

%:::z

numeric time zone with : to necessary precision (e.g., -04, +05:30)

%Z

alphabetic time zone abbreviation (e.g., EDT)

Examples date +"%m-%d-%y" 02-27-07 Display date as mm/dd/yy format. date +"%D" Display time only date +"%T" 19:55:04 Display locale's 12-hour clock time date +"%r" 07:56:05 PM Display time in HH:MM format date +"%H-%M" 00-50 date “+%m-%d-%Y %B” 02-10-2010 Februrary

Examples

Find last month

PREV_MONTH=`date +'%m' -d 'last month'`

if today' s date is 11-04-2014, it will give 03.

PREV_MONTH_YEAR=`date +'%Y' -d 'last month'`

if today 's date is 11-04-2014, it will give 2014.

if today' s date is 05-01-2014, it will give 2013.