How do I get the help manual for office

I want to know the short cut to add a date to spread sheet.

Libreoffice documentation.

What kind of date do you want to insert in your spreadsheet? Give more informations so that someone can help you.

In Download page there is an option to download the help for off line use.

Shortcut is Ctrl+;

You can see all shortcuts in Menu/Tools/Customize/Keyboard