diff --git a/src/MDRequirementsSet.php b/src/MDRequirementsSet.php
index 2d0fb7e..ca6b0b5 100644
--- a/src/MDRequirementsSet.php
+++ b/src/MDRequirementsSet.php
@@ -23,6 +23,9 @@ final class MDRequirementsSet {
     // Object images need to be at least 500 px wide
     const MIN_OBJECT_IMAGE_HEIGHT = 540;
 
+    const TIME_EARLIEST_YEAR = -6000000000;
+    const TIME_LATEST_YEAR = 2099;
+
     const MIMETYPES_USER_PROFILE_IMG = ['image/jpeg', 'image/jpg'];
 
     const MIMETYPES_OBJECT_IMAGE = ['image/jpeg', 'image/jpg'];