Log out users from every where

Firstly if you’d just like everyone to have to log in again you can void all of your cookies at once by changing your cookie hashes in your wordpress config file.

The lines that look like this:

define('AUTH_KEY',         ':u(rb=Ys8*2x^rVisqX(9=10a*.euPdYEBo6p_ZBB2CDG|rv~Ju)sh+6@=L6p_:l');
define('SECURE_AUTH_KEY',  '-`<iUz(4olJ`m&}1kA*{v&OX;Kq?W+!7ppF!tWb}cM<R=d<s=(oL]]04%AA@juZB');
define('LOGGED_IN_KEY',    '$KA]84n3ZT}v6m7c:r+!6l}R||)<_$3GxJ%F6Y?MopvxydJ@PRcmZ0-Hyq(EuEZt');
define('NONCE_KEY',        'qT=]!^BARWEMUD(G6]#~q$PAv-N[#^uE991w7HJNN<*mXavH)@o0TkFKVFUNIDN#');
define('AUTH_SALT',        'c W#7TWk{L1+n0A+^:|FHYL#-;*#<8U :v%>~S!45$bbYM09Iwe;@=uk^xeJd_D`');
define('SECURE_AUTH_SALT', 'h3&dgYcQE0uTaxd5bX$&1wC]yKP^?W8#q#>IJ*)ggf_Rc+6f+oZa?#JVS[HmO?=O');
define('LOGGED_IN_SALT',   '_L:n)>u>-31YK_ftTp_ZV>-y)qG)so|sOoWgYC9Ju!q_!%f.60g?I~]~lNZ6&o!0');
define('NONCE_SALT',       '.KI_*}ONxh/uwZv~!qYqOW+OL;?qvgaEqayN8>i+B.WY$e}+M9.Xqxwlf+?v 1k=');

This website is a good tool for generating new secure keys to put in.

If you want to change the amount of time you can be logged in for you can use the below code in your themes functions.php:

add_filter( 'auth_cookie_expiration', 'keep_me_logged_in_for' );

function keep_me_logged_in_for( $expirein ) {
    return 86400; // time in seconds
}