21 files declare their use of TimeInterface in Drupal 8

AccountForm.php in core/modules/user/src/AccountForm.php

BookOutlineForm.php in core/modules/book/src/Form/BookOutlineForm.php

CommentForm.php in core/modules/comment/src/CommentForm.php

ContentEntityForm.php in core/lib/Drupal/Core/Entity/ContentEntityForm.php

ContentEntityFormTest.php in core/tests/Drupal/Tests/Core/Entity/ContentEntityFormTest.php

Cron.php in core/lib/Drupal/Core/Cron.php

EntityResource.php in core/modules/jsonapi/src/Controller/EntityResource.php

MenuLinkContentForm.php in core/modules/menu_link_content/src/Form/MenuLinkContentForm.php

MessageForm.php in core/modules/contact/src/MessageForm.php

NodeForm.php in core/modules/node/src/NodeForm.php

NodeRevisionRevertForm.php in core/modules/node/src/Form/NodeRevisionRevertForm.php

NodeRevisionRevertTranslationForm.php in core/modules/node/src/Form/NodeRevisionRevertTranslationForm.php

OverridesEntityForm.php in core/modules/layout_builder/src/Form/OverridesEntityForm.php

ProviderRepository.php in core/modules/media/src/OEmbed/ProviderRepository.php

ReplicaKillSwitch.php in core/lib/Drupal/Core/Database/ReplicaKillSwitch.php

SaveAction.php in core/lib/Drupal/Core/Action/Plugin/Action/SaveAction.php

SaveComment.php in core/modules/comment/src/Plugin/Action/SaveComment.php

SaveNode.php in core/modules/node/src/Plugin/Action/SaveNode.php

WorkspaceDeleteForm.php in core/modules/workspaces/src/Form/WorkspaceDeleteForm.php

WorkspaceDeployForm.php in core/modules/workspaces/src/Form/WorkspaceDeployForm.php

WorkspaceForm.php in core/modules/workspaces/src/Form/WorkspaceForm.php