NAME:
    rdate  --display date and time
SYNOPSIS:
    rdate [-f] [time format] [-c] [colculation format] [-d] [input_time] [input_time_format]
DESCRIPTION:

    -c: value is hour/day/week/month/year,plus +/-,plus a number which is number to colculate

    -l: obtain a number which is last day of month

    -d:
        input_time: enter a time string
        input_time_format: enter a time format for input time,default %Y%m%d or %Y-%m-%d

    -f:

     %A    is replaced by national representation of the full weekday name.
     %a    is replaced by national representation of the abbreviated weekday name.
     %B    is replaced by national representation of the full month name.
     %b    is replaced by national representation of the abbreviated month name.
     %C    is replaced by (year / 100) as decimal number; single digits are preceded by a zero.
     %c    is replaced by national representation of time and date.
     %D    is equivalent to ``%m/%d/%y''.
     %d    is replaced by the day of the month as a decimal number (01-31).
     %E* %O*
            POSIX locale extensions.  The sequences %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy are supposed to provide alternate
            representations.
            Additionally %OB implemented to represent alternative months names (used standalone, without day mentioned).
     %e    is replaced by the day of the month as a decimal number (1-31); single digits are preceded by a blank.
     %F    is equivalent to ``%Y-%m-%d''.
     %G    is replaced by a year as a decimal number with century.  This year is the one that contains the greater part of the week (Monday as the first day of
            the week).
     %g    is replaced by the same year as in ``%G'', but as a decimal number without century (00-99).
     %H    is replaced by the hour (24-hour clock) as a decimal number (00-23).
     %h    the same as %b.
     %I    is replaced by the hour (12-hour clock) as a decimal number (01-12).
     %j    is replaced by the day of the year as a decimal number (001-366).
     %k    is replaced by the hour (24-hour clock) as a decimal number (0-23); single digits are preceded by a blank.
     %l    is replaced by the hour (12-hour clock) as a decimal number (1-12); single digits are preceded by a blank.
     %M    is replaced by the minute as a decimal number (00-59).
     %m    is replaced by the month as a decimal number (01-12).
     %n    is replaced by a newline.
     %O*   the same as %E*.
     %p    is replaced by national representation of either ante meridiem (a.m.)  or post meridiem (p.m.)  as appropriate.
     %R    is equivalent to ``%H:%M''.
     %r    is equivalent to ``%I:%M:%S %p''.
     %S    is replaced by the second as a decimal number (00-60).
     %s    is replaced by the number of seconds since the Epoch, UTC (see mktime(3)).
     %T    is equivalent to ``%H:%M:%S''.
     %t    is replaced by a tab.
     %U    is replaced by the week number of the year (Sunday as the first day of the week) as a decimal number (00-53).
     %u    is replaced by the weekday (Monday as the first day of the week) as a decimal number (1-7).
     %V    is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (01-53).  If the week containing January 1 has
            four or more days in the new year, then it is week 1; otherwise it is the last week of the previous year, and the next week is week 1.
     %v    is equivalent to ``%e-%b-%Y''.
     %W    is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (00-53).
     %w    is replaced by the weekday (Sunday as the first day of the week) as a decimal number (0-6).
     %X    is replaced by national representation of the time.
     %x    is replaced by national representation of the date.
     %Y    is replaced by the year with century as a decimal number.
     %y    is replaced by the year without century as a decimal number (00-99).
     %Z    is replaced by the time zone name.
     %z    is replaced by the time zone offset from UTC; a leading plus sign stands for east of UTC, a minus sign for west of UTC, hours and minutes follow with
            two digits each and no delimiter between them (common form for RFC 822 date headers).
     %+    is replaced by national representation of the date and time (the format is similar to that produced by date(1)).
     %-*   GNU libc extension.  Do not do any padding when performing numerical outputs.
     %_*   GNU libc extension.  Explicitly specify space for padding.
     %0*   GNU libc extension.  Explicitly specify zero for padding.
     %%    is replaced by `%'.

EXAMPLE:
     rdate                                              --2017-10-23 11:04:51 Monday
     rdate -f "%Y-%m_%d"                                --2017-10-23
     rdate -f "%Y-%m_%d" -c "day-3"                     --2017-10-20
     rdate -f "%Y-%m_%d" -c "day+3"                     --2017-10-26
     rdate -f "%Y-%m_%d" -c "month+3"                   --2017-7-23
     rdate -f "%Y-%m_%d" -c "year+3"                    --2020-7-23
     rdate -c "week - 1" -f "%Y-%m-%d %V"               --2018-02-15 07
     rdate -c "day - 30" -f "%Y-%m-%d" -l               --2018-01-31
     rdate -d "1972-01-31" "%Y-%m-%d"                   --1972-01-31 00:00:00 Monday