Using the latest version of the Simple Clock in Moodle 2.9 gives a deprecation warning with debugging turned on to Developer.

get_timezone_offset() is deprecated, use PHP DateTimeZone instead

line 67 of /lib/deprecatedlib.php: call to debugging()
line 193 of /blocks/simple_clock/block_simple_clock.php: call to get_timezone_offset()
line 288 of /blocks/moodleblock.class.php: call to block_simple_clock->get_content()
line 230 of /blocks/moodleblock.class.php: call to block_base->formatted_contents()
line 971 of /lib/blocklib.php: call to block_base->get_content_for_output()
line 1023 of /lib/blocklib.php: call to block_manager->create_block_contents()
line 335 of /lib/blocklib.php: call to block_manager->ensure_content_created()
line 36 of /theme/formal_white/layout/frontpage.php: call to block_manager->region_has_content()
line 1015 of /lib/outputrenderers.php: call to include()
line 945 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
line 112 of /index.php: call to core_renderer->header()