Record date and time information at login.

record-current-datetime-at-login.php

<?php
add_action( 'wp_login', 'record_current_datetime_at_login', 10, 2 );
/**
 * Record Time and Date at login as a readable string.
 * Save in user meta.
 *
 * @param  string $user_login login_name
 * @param  object $user       WP_User object
 * @return string             Date, time, timezone, offset
 */
function record_current_datetime_at_login( $user_login, $user ) {
	$time =  date_i18n( get_option( 'date_format' ), time() ) . ' ' . get_option( 'timezone_string' ) . ' ' . date_i18n( get_option( 'time_format' ), time() ) . ' ' . get_option( 'gmt_offset' ) . ' hours offset';
	update_user_meta( $user->ID, $user_login . '_last_login_' . $user->ID, $time);
}