Problem: Front end browser throws error of "Internal error. Please try again later." after selecting service and worker that has no more slots available in month selected in calendar widget. Cause: Back end server error is thrown:

[Tue Aug 30 19:00:55.114813 2022] [php:notice] [pid 355914] [client 109.241.167.138:52206] B\xc5\x82\xc4\x85d Incorrect DATE value: '-00-01' bazy danych WordPressa podczas wykonywania zapytania SELECT * FROM wp_ea_connections WHERE \n\t\t\tlocation=1 AND \n\t\t\tservice=14 AND \n\t\t\tworker=15 AND \n\t\t\tday_of_week LIKE '%Tuesday%' AND \n\t\t\tis_working = 1 AND \n\t\t\t(day_from IS NULL OR day_from <= '-00-01') AND \n\t\t\t(day_to IS NULL OR day_to >= '-00-01') wys\xc5\x82anego przez do_action('wp_ajax_nopriv_ea_month_status'), WP_Hook->do_action, WP_Hook->apply_filters, EAAjax->ajax_month_status, EAReport->get_available_dates, EAReport->get_whole_month_slots, EALogic->get_open_slots, W3TC\\DbCache_WpdbNew->query, W3TC\\DbCache_WpdbInjection_QueryCaching->query, W3TC\\_CallUnderlying->query, W3TC\\DbCache_WpdbNew->query, W3TC\\DbCache_WpdbInjection->query, W3TC\\DbCache_WpdbNew->default_query, referer: https://poradniabraincare.pl/umow/

Indicating use of wrong date notation like day_from <= '-00-01'. Way to reproduce:

1. Open reservation applet and select service + worker that has no more available slots for month displayed

In our case:

1. open https://poradniabraincare.pl/umow.
2. In Usługa select "Integracja sensoryczna"
3. In Specjalista select "Terapeutka Manuela"
4. Observe Internal Error popup