Unix date format is needed  in the scripts, timestamped log files and  script generated reports .  This article attempts to simply date formatting with several examples .  Date command in Unix is used to format date as well as time . First portion of this article covers Date  function and the second portion has the  time function covered .

Unix  Basic date format

$date “+<Parameter><seprator><Parameter><seprator><Parameter>

Where Parameters  is  any one or more Parameter from the list below and separator is a any field separator like hyphen( – ) , slash , colon :   and it is optional.

Unix Date Format Examples

lets get the parameter for year , month and date and produce a hyphen separated date format

$date “+%Y-%m-%d”

2010-02-10

%Y is keyword for four digit year
%m is keyword for two digit month
%d is keyword for two digit date
Hyphen is separator here .

If you change the separator here to slash the format would look like

$date “+%Y/%m/%d”
2010/02/10

You can switch date keyword anyway you want , if you need month first and year last ,

$date “+%m-%d-%Y”
02-10-2010

Weekdays

You can have additional weekday information in your date with %A as

$date “+%m-%d-%Y %A”
02-10-2010 Wednesday

or

$date “+%A %m-%d-%Y”
Wednesday 02-10-2010

These are options you can select for weekday

%a weekday, abbreviated Wed
%A weekday, full Wednesday
%d day of the month (dd), zero padded 10
%e day of the month (dd) 10
%j day of year, zero padded 000-366
%u day of week starting with Monday (1), i.e. mtwtfss 3
%w day of week starting with Sunday (0), i.e. smtwtfs 3

Month

You can have additional month information in your date with %B as

$date “+%m-%d-%Y %B”
02-10-2010 Februrary

or

$date “+%B %m-%d-%Y”
February 02-10-2010

These are options you can select for month

%m mm month as two digits
%b Mon, locale’s abbreviated Feb
%B locale’s full month, variable length February

Year

You can have additional year information as two digit or four digit with %y or %Y as

$date “+%m-%d-%y ”
02-10-10

or

$date “+%m-%d-%Y ”
02-10-2010

These are options you can select for year

%y yy two digit year 00–99
%Y ccyy year 2010

Additional date format parameters which can be used :

Week

%U week number Sunday as first day of week 01–53
%W week number Monday as first day of week 01–53
%V week of the year 01–53

Century

%C cc century 00–99

Date

%D mm/dd/yy 02/10/10
%x locale’s date representation (mm/dd/yy) 02/10/2010
%F %Y-%m-%d 2010-02-10

Date and Time time stamp

%c locale’s date and time Wed Feb 10 10:02:33 PST 2010

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Time function

Time function is simple to use and date command is used to format & display time as well . You can use date and time parameters to format your date time stamp as per your requirment

A simple time stamp with date can be generated as :

$date “+%c”
%c locale’s date and time Sat Nov 04 12:02:33 EST 1989

Date function have some preformated time stamps to make things easier

Example :

$date “+%r”
05:28:55 PM

More preformated options :

%R hours, minutes (24 hour clock) hh:mm e.g. 17:28
%T hours, minutes, seconds (24-hour clock) 17:28:55
%X locale’s time representation (%H:%M:%S) 05:28:55 PM

Custom time format

Examples

Time stamp with 12 hr clock

$date “+%l:%M:%S
5:22:45

Time stamp with 24 hr clock

$date “+%H:%M:%S”
20:22:45

Time stamp with AM/PM

$date “+%l:%M:%S %p”
5:22:45  PM

Additional date time parameters :

Hours
%l (Lowercase L) hour (12 hour clock) 8
%I (Uppercase I) hour (12 hour clock) zero padded 08
%k hour (24 hour clock) 20
%H hour (24 hour clock) zero padded 20
%p locale’s upper case AM or PM (blank in many locales) PM
%P locale’s lower case am or pm (really!) pm

Minutes
%M MM minutes 28

Seconds
%s seconds since 00:00:00 1970-01-01 UTC (Unix epoch) 1265833735
%S SS second 00–60
%N nanoseconds 000000000–999999999

Time zone
%z -zzzz RFC-822 style numeric timezone -0500
%Z time zone (e.g., EDT) nothing if no time zone is determinable EST