How do I show a message with username and date at login?

If you want to see the message when you open the terminal or after you are login in tty1-6, just put this line at the end of ~/.bashrc file (open it from terminal with gedit ~/.bashrc):

echo "Hello $USER, today's date is $(date +"%A, %d-%m-%y")"

If you want to see the message after you are login in GUI, do the following:

1. Create a new file name_and_date.sh:

   gedit ~/bin/name_and_date.sh
   

2. If you want to get a desktop notification, put next 2 lines inside:

   #!/bin/bash
   notify-send "Hello" "Hello $USER, today's date is $(date +"%A, %d-%m-%y")"
   

   Alternatively, if you want a popup (message box) to show up, put next 2 lines inside:

   #!/bin/bash
   zenity --info --title "Hello" --text "Hello $USER, today's date is $(date +"%A, %d-%m-%y")"
   

3. Save the file and close it.

4. Make the file exacutable:

   chmod +x ~/bin/name_and_date.sh
   

5. Search in Dash for Startup Applications, open it and click Add.
6. Under name type "Show my name and date" or something you will recognise.
7. Under command type: /home/$USER/bin/name_and_date.sh (change $USER with your user name).
8. Under comment (if you want), type a brief description.