I get this error please help

Hello i was wondering how i could fix this bug:

'calendar_plugin_style: A date argument is required when using the calendar style, but it is missing or is not using the default date.'

in calendar_plugin_style->render() (regel 232 van /var/www/vhosts/ototoko.nl/httpdocs/sites/all/modules/calendar/includes/calendar_plugin_style.inc).

Early thanks,
Jelmar Maatman