Fatal error: Uncaught TypeError: sd_iso8601_from_wp(): Argument #2 ($default_time) must be of type string, null given, called in /home/sciencedays7/sciencedays.jp/public_html/wp-content/themes/swell_child/includes/schema/article.php on line 37 and defined in /home/sciencedays7/sciencedays.jp/public_html/wp-content/themes/swell_child/includes/schema/common.php:152 Stack trace: #0 /home/sciencedays7/sciencedays.jp/public_html/wp-content/themes/swell_child/includes/schema/article.php(37): sd_iso8601_from_wp('2020-01-29T07:0...', NULL, false) #1 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/class-wp-hook.php(324): output_article_structured_data('') #2 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array) #3 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #4 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/general-template.php(3192): do_action('wp_head') #5 /home/sciencedays7/sciencedays.jp/public_html/wp-content/themes/swell/header.php(10): wp_head() #6 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/template.php(810): require_once('/home/scienceda...') #7 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/template.php(745): load_template('/home/scienceda...', true, Array) #8 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/general-template.php(48): locate_template(Array, true, true, Array) #9 /home/sciencedays7/sciencedays.jp/public_html/wp-content/themes/swell/single.php(4): get_header() #10 /home/sciencedays7/sciencedays.jp/public_html/wp-includes/template-loader.php(106): include('/home/scienceda...') #11 /home/sciencedays7/sciencedays.jp/public_html/wp-blog-header.php(19): require_once('/home/scienceda...') #12 /home/sciencedays7/sciencedays.jp/public_html/index.php(17): require('/home/scienceda...') #13 {main} thrown in /home/sciencedays7/sciencedays.jp/public_html/wp-content/themes/swell_child/includes/schema/common.php on line 152