Linux

You could write a simple python script using datetime and pyperclip. Datetime would supply the date format and pyperclip to copy that to your clipboard. You could setup a key binding to call the script then [Ctrl + v] to paste.

I believe all linix distros have python installed OTB.

There are probably a bash solution but my bash is rubbish.

Edit:

The bash solution that has been provided is the best option IMO. I just thought I should provide the code for my solution so you have options. This python script is easily extendable / customizable. All this depends in you installing the python module pyperclip. datetime should be part if the standard python library so you dont have to install it.

installing pyperclip with pip.

pip install pyperclip

The script:

#!/usr/bin/env python3
"""A simple script to copy a formatted datetime string to the users clipboard"""

import datetime
import pyperclip

def clipboard_timestamp(initials) -> None:
    """Function to create a formatted timestamp string to users clipboard.

    Arguments:
       initials: Uses the provided string during formatting of the timestamp."""

    time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    pyperclip.copy(f"{initials} {time}")

if __name__ == "__main__":

    clipboard_timestamp('ABC')

The above script also adds the hours minutes and seconds to the timestamp. If not needed remove the %H:%M:%S. Dont forget to edit anything that you want like the 'ABC' near the end.

Save script somewhere. I usually save personal scripts to ~/.local/bin so they are out of the way. I used the name clipboard_timestamp.py Doesn't really matter as long as you remember the name. Next you have 2 options. You can make the script executable using chmod a+x clipboard_timestamp.py. If you dont want to take this step you will have to tell the shortcut that python is executing the script by prefacing the script's full path with python like so python ~/.local/bin/clipboard_timestamp.py If you made the script executable you just use ~/.local/bin/clipboard_timestamp.py.

I use KDE but your system should be similar-ish. in your desktop's setting's search for keyboard and you should see something that says something like shortcuts. Add New -> Command or Script. Point this to your newly saved python script /.local/bin/clipboard_timestamp.py. Then you choose the keystroke combination.