Note: this list is generated by looking for the string for this theme hook, so it may include some references that are not actually using this theme hook.

DateFieldTestCase::dateForm in core/modules/date/tests/date_field.test
Tests that date field functions properly on the node form.
DateFieldTestCase::testField in core/modules/date/tests/date_field.test
@todo.
DateFieldTokenTestCase::testDateFieldToken in core/modules/date/tests/date_field.test
Tests that date field tokens function properly.
DateTimezoneTestCase::testMultiUserTimezone in core/modules/date/tests/date_timezone.test
Validates timezone handling with a multi-value date field.
DateTimezoneTestCase::testTimezone in core/modules/date/tests/date_timezone.test
Creates one of each type of date field and check timezone handling in each.
DateUITestCase::dateForm in core/modules/date/tests/date.test
DateUITestCase::testFieldUI in core/modules/date/tests/date.test
DateValidationTestCase::checkGranularity in core/modules/date/tests/date_validation.test
Confirms that fields missing the time granularity are accepted.
DateValidationTestCase::dateRangeTests in core/modules/date/tests/date_validation.test
Tests for date ranges.
DateValidationTestCase::malFormedDate in core/modules/date/tests/date_validation.test
Attempt to create a node with a malformed date and ensure it fails.
DateValidationTestCase::testValidation in core/modules/date/tests/date_validation.test
Test validation on each type of date widget.
DateViewsTestCase::testDateViewsFields in core/modules/date/tests/date_views.test
date_combo_element_process in core/modules/date/date.elements.inc
Process an individual date element.
date_field_widget_info in core/modules/date/date.field.inc
Implements hook_field_widget_info().
date_field_widget_properties_alter in core/modules/date/date.module
Implements hook_field_widget_properties_alter().
date_input_date in core/modules/date/date.module
Wrapper function around each of the widget types for creating a date object.
date_text_element_process in core/modules/date/date.elements.inc
Text date input form.
date_theme in core/modules/date/date.module
Implements hook_theme().
date_views_filter_handler_simple::widget_options in core/modules/date/views/date_views_filter_handler_simple.inc
Date selection options.
FieldTokenTestCase::setUp in core/modules/field/tests/field.test
Sets up a Backdrop site for running functional and integration tests.
_date_element_info in core/modules/date/date.elements.inc
Implements hook_element_info().