9 files declare their use of WebformDateHelper in Webform 8.5

DateBase.php in src/Plugin/WebformElement/DateBase.php

ScheduleEmailWebformHandler.php in modules/webform_scheduled_email/src/Plugin/WebformHandler/ScheduleEmailWebformHandler.php

webform.theme.template.inc in includes/webform.theme.template.inc

Preprocessors and helper functions to make theming easier.

webform.tokens.inc in ./webform.tokens.inc

Builds placeholder replacement tokens for webforms and submissions.

WebformEntityReferenceWidgetTrait.php in src/Plugin/Field/FieldWidget/WebformEntityReferenceWidgetTrait.php

WebformEntitySettingsFormForm.php in src/EntitySettings/WebformEntitySettingsFormForm.php

WebformEntitySettingsSubmissionsForm.php in src/EntitySettings/WebformEntitySettingsSubmissionsForm.php

WebformSubmissionLimitBlock.php in src/Plugin/Block/WebformSubmissionLimitBlock.php

webform_demo_event_registration.install in modules/webform_demo/webform_demo_event_registration/webform_demo_event_registration.install

Install, update and uninstall functions for the webform demo event registration module.