PHP Fata error

PHP Fatal error:? Uncaught Error: Call to undefined function cal_days_in_month() in /var/www/html/wp-content/plugins/mwb-bookings-for-woocommerce/public/class-mwb-bookings-for-woocommerce-public.php:93\nStack trace:

#0 /var/www/html/wp-includes/class-wp-hook.php(324): Mwb_Bookings_For_Woocommerce_Public->mbfw_public_enqueue_scripts(”)

#1 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)

#2 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)

#3 /var/www/html/wp-includes/script-loader.php(2262): do_action(‘wp_enqueue_scri…’)

#4 /var/www/html/wp-includes/class-wp-hook.php(324): wp_enqueue_scripts(”)

#5 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)

#6 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)

#7 /var/www/html/wp-includes/general-template.php(3052): do_action(‘wp_head’)

#8 /var/www/html/wp-includes/template-canvas.php(17): wp_head()

#9 /var/www/html/wp-includes/template-loader.php(106): include(‘/var/www/html/w…’)

#10 /var/www/html/wp-blog-header.php(19): require_once(‘/var/www/html/w…’)

#11 /var/www/html/index.php(17): require(‘/var/www/html/w…’)

#12 {main}

? thrown in /var/www/html/wp-content/plugins/mwb-bookings-for-woocommerce/public/class-mwb-bookings-for-woocommerce-public.php on line 93