date_combo_validate in core/modules/date/date.elements.inc

Validate and update a combo element.

date_parts_element in core/modules/date/date.elements.inc

Creates form elements for one or more date parts.

date_popup_element_value_callback in core/modules/date/date.elements.inc

Element value callback for date_popup element.

date_popup_validate in core/modules/date/date.elements.inc

Massage the input values back into a single date.

date_select_element_value_callback in core/modules/date/date.elements.inc

Element value callback for date_select element.

date_select_validate in core/modules/date/date.elements.inc

Validation function for date selector.

date_text_element_value_callback in core/modules/date/date.elements.inc

Element value callback for date_text element.

date_text_validate in core/modules/date/date.elements.inc

Validation for text input.