How does one change Terminal.app profile for all open tabs using a keyboard shortcut?
Create an AppleScript like this one, and call it something like TerminalNightMode:

tell application "Terminal"
    set current settings of tabs of windows to settings set "Pro"
end tell


You can replace the "Pro" setting with the setting name of your choice. When you run this AppleScript, it will change the settings for all the tabs in all windows. I recommend putting this script on the dock for easy access. Likewise, you can make another script for day mode.