Questions[coreutils](ubuntu)

Upon reading GNU Core Utilities - Wikipedia, I find multiple sum

me@alpha:~$ cksum nohup.out 
4104911401 101860700 nohup.out
me@alpha:~$ b2sum nohup.out 
468c86394c5c4be04d0bce3b98584197b0c3f4cbb630144818f9d77d48ab7296e4c53db481b6bdd7c46dd5203d3f016d9ef01b126806e04be5003aeebb1bc6
22  nohup.out                                                                                                                
me@alpha:~$ sum nohup.out 
37767 99474
me@alpha:~$ sha1sum nohup.out 
79106925d593e18bd148ba94a6e4fb9da02e8c47  nohup.out
 me@alpha:~$ md5sum nohup.out 
3be4b17f18e4715d849a31ae482565cf  nohup.out

I started learning linux months ago, should I have to distinguish them and utilize them in daily operation?

I know how to use sleep 5m for 5 minutes.

How would I use it for say 7 mins 30 seconds?

How do I change the format of date command by modifying LC_TIME in locale?

Currently the day of month uses %e format. I need it to be displayed in %d format.

Below is the Current Format:

#date
Thu Aug 9 18:26:11 IST 2018

Expected format:

#date
Thu Aug 09 18:26:11 IST 2018

Here is my locale:

#locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE=en_IN
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

LC_TIME section in /usr/share/i18n/locales/en_US:

    LC_TIME
abday   "Sun";"Mon";"Tue";"Wed";"Thu";"Fri";"Sat"
day "Sunday";/
    "Monday";/
    "Tuesday";/
    "Wednesday";/
    "Thursday";/
    "Friday";/
    "Saturday"

week 7;19971130;1
abmon   "Jan";"Feb";/
    "Mar";"Apr";/
    "May";"Jun";/
    "Jul";"Aug";/
    "Sep";"Oct";/
    "Nov";"Dec"
mon "January";/
    "February";/
    "March";/
    "April";/
    "May";/
    "June";/
    "July";/
    "August";/
    "September";/
    "October";/
    "November";/
    "December"
% Appropriate date and time representation (%c)
d_t_fmt "%a %d %b %Y %r %Z"
%
% Appropriate date representation (%x)
d_fmt   "%m//%d//%Y"
%
% Appropriate time representation (%X)
t_fmt   "%r"
%
% Appropriate AM/PM time representation (%r)
t_fmt_ampm "%I:%M:%S %p"
%
% Strings for AM/PM
%
am_pm   "AM";"PM"
date_fmt "%F %Z"
END LC_TIME

Please let me know what I can do in order to get the expected format.

NOTE: I need to execute just date command without any formatting options.

I've been trying to find the difference between using the dir and ls commands in terminal. I know ls is the traditional UNIX method of viewing the files in a directory, and that dir is the windows command prompt equivalent, but both commands work in terminal.

If I type in dir, it displays the files and folders in the directory, and if I type ls, it does the same, except with content highlighting. Both commands accept options (i.e. ls -a and dir -a both return all files and folders and hidden files.

So does anyone know what the difference is and why both dir and ls are used?

Otherwise, is there any alternative command line utility that can achieve this?