start Date could not be converted to date object.Check date and global timezone.
bool(false) object(DateTimeZone)#6803 (2) { ["timezone_type"]=> int(3) ["timezone"]=> string(13) "Europe/Vienna" } Fatal error: Uncaught TypeError: date_modify(): Argument #1 ($object) must be of type DateTime, bool given in /home/.sites/74/site1164/web/website/wp-content/plugins/amr-ical-events-list/includes/amr-ical-events-list-main.php:2092 Stack trace: #0 /home/.sites/74/site1164/web/website/wp-content/plugins/amr-ical-events-list/includes/amr-ical-events-list-main.php(2092): date_modify(false, '-720000000 days') #1 /home/.sites/74/site1164/web/website/wp-content/plugins/amr-ical-events-list/includes/amr-ical-events-list-main.php(2210): amr_GET_params(Array) #2 /home/.sites/74/site1164/web/website/wp-includes/shortcodes.php(394): amr_do_ical_shortcode(Array, '', 'ical') #3 [internal function]: do_shortcode_tag(Array) #4 /home/.sites/74/site1164/web/website/wp-includes/shortcodes.php(266): preg_replace_callback('/\\[(\\[?)(ical)(...', 'do_shortcode_ta...', '[ical https://s...') #5 /home/.sites/74/site1164/web/website/wp-includes/class-wp-hook.php(307): do_shortcode('[ical https://s...') #6 /home/.sites/74/site1164/web/website/wp-includes/plugin.php(189): WP_Hook->apply_filters('[ical https://s...', Array) #7 /home/.sites/74/site1164/web/website/wp-includes/post-template.php(253): apply_filters('the_content', '[ical https://s...') #8 /home/.sites/74/site1164/web/website/wp-content/themes/twentyseventeen/template-parts/page/content-page.php(22): the_content() #9 /home/.sites/74/site1164/web/website/wp-includes/template.php(772): require('/home/.sites/74...') #10 /home/.sites/74/site1164/web/website/wp-includes/template.php(716): load_template('/home/.sites/74...', false, Array) #11 /home/.sites/74/site1164/web/website/wp-includes/general-template.php(204): locate_template(Array, true, false, Array) #12 /home/.sites/74/site1164/web/website/wp-content/themes/twentyseventeen/page.php(28): get_template_part('template-parts/...', 'page') #13 /home/.sites/74/site1164/web/website/wp-includes/template-loader.php(106): include('/home/.sites/74...') #14 /home/.sites/74/site1164/web/website/wp-blog-header.php(19): require_once('/home/.sites/74...') #15 /home/.sites/74/site1164/web/website/index.php(17): require('/home/.sites/74...') #16 {main} thrown in /home/.sites/74/site1164/web/website/wp-content/plugins/amr-ical-events-list/includes/amr-ical-events-list-main.php on line 2092