diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1e794b53..ac67542f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # @digitalbazaar/cborld ChangeLog
 
+## 8.0.2 - 2025-mm-dd
+
+### Fixed
+- Properly encode/decode dates from before the epoch.
+
 ## 8.0.1 - 2025-05-21
 
 ### Fixed
diff --git a/lib/codecs/ValueEncoder.js b/lib/codecs/ValueEncoder.js
index 642ca83e..86c79ce1 100644
--- a/lib/codecs/ValueEncoder.js
+++ b/lib/codecs/ValueEncoder.js
@@ -1,5 +1,5 @@
 /*!
- * Copyright (c) 2024 Digital Bazaar, Inc. All rights reserved.
+ * Copyright (c) 2024-2025 Digital Bazaar, Inc. All rights reserved.
  */
 import {
   bytesFromInt,
@@ -37,7 +37,8 @@ export class ValueEncoder extends CborldEncoder {
       const bytes = toBytes({intValue});
       return new Token(Type.bytes, bytes);
     }
-    return new Token(Type.uint, intValue);
+    const tokenType = intValue >= 0 ? Type.uint : Type.negint;
+    return new Token(tokenType, intValue);
   }
 
   static createEncoder({value, converter, termInfo, termType} = {}) {
diff --git a/lib/codecs/XsdDateEncoder.js b/lib/codecs/XsdDateEncoder.js
index cca0d4cf..ecada4bf 100644
--- a/lib/codecs/XsdDateEncoder.js
+++ b/lib/codecs/XsdDateEncoder.js
@@ -1,5 +1,5 @@
 /*!
- * Copyright (c) 2021-2024 Digital Bazaar, Inc. All rights reserved.
+ * Copyright (c) 2021-2025 Digital Bazaar, Inc. All rights reserved.
  */
 import {Token, Type} from 'cborg';
 import {CborldEncoder} from './CborldEncoder.js';
@@ -21,7 +21,8 @@ export class XsdDateEncoder extends CborldEncoder {
       // compression would be lossy, do not compress
       return new Token(Type.string, value);
     }
-    return new Token(Type.uint, secondsSinceEpoch);
+    const tokenType = secondsSinceEpoch >= 0 ? Type.uint : Type.negint;
+    return new Token(tokenType, secondsSinceEpoch);
   }
 
   static createEncoder({value} = {}) {
diff --git a/lib/codecs/XsdDateTimeEncoder.js b/lib/codecs/XsdDateTimeEncoder.js
index 37e539bb..a3172047 100644
--- a/lib/codecs/XsdDateTimeEncoder.js
+++ b/lib/codecs/XsdDateTimeEncoder.js
@@ -1,5 +1,5 @@
 /*!
- * Copyright (c) 2021-2024 Digital Bazaar, Inc. All rights reserved.
+ * Copyright (c) 2021-2025 Digital Bazaar, Inc. All rights reserved.
  */
 import {Token, Type} from 'cborg';
 import {CborldEncoder} from './CborldEncoder.js';
@@ -14,7 +14,8 @@ export class XsdDateTimeEncoder extends CborldEncoder {
   encode() {
     const {value, parsed} = this;
     const secondsSinceEpoch = Math.floor(parsed / 1000);
-    const secondsToken = new Token(Type.uint, secondsSinceEpoch);
+    const tokenType = secondsSinceEpoch >= 0 ? Type.uint : Type.negint;
+    const secondsToken = new Token(tokenType, secondsSinceEpoch);
     const millisecondIndex = value.indexOf('.');
     if(millisecondIndex === -1) {
       const expectedDate = new Date(
diff --git a/tests/roundtrip.spec.js b/tests/roundtrip.spec.js
index de8a369d..d0e27a12 100644
--- a/tests/roundtrip.spec.js
+++ b/tests/roundtrip.spec.js
@@ -854,6 +854,108 @@ describe('cborld round trip', () => {
     expect(decodedDocument).to.eql(jsonldDocument);
   });
 
+  it('should handle wide dateTime range', async () => {
+    const CONTEXT = {
+      '@context': {
+        date: {
+          '@id': 'ex:date',
+          '@type': 'http://www.w3.org/2001/XMLSchema#dateTime'
+        },
+      }
+    };
+    const jsonldDocument = {
+      '@context': CONTEXT['@context'],
+      date: [
+        '-1000-01-01T00:00:00Z',
+        '0-01-01T00:00:00Z',
+        '1000-01-01T00:00:00Z',
+        '1000-01-01T00:00:00.123Z',
+        '1960-01-01T00:00:00Z',
+        '1960-01-01T23:59:59Z',
+        '1969-12-31T23:59:59Z',
+        '1970-01-01T00:00:00Z',
+        '1970-01-01T00:00:01Z',
+        '1970-12-31T23:59:59Z',
+        '2000-01-01T00:00:00Z',
+        '3000-01-01T00:00:00Z',
+        '3000-01-01T00:00:00.123Z',
+        '10000-01-01T00:00:00Z'
+        // TODO: increase possible xsd:dateTime value coverage
+      ]
+    };
+
+    const documentLoader = url => {
+      throw new Error(`Refused to load URL "${url}".`);
+    };
+
+    const typeTable = new Map(TYPE_TABLE);
+
+    const cborldBytes = await encode({
+      jsonldDocument,
+      format: 'cbor-ld-1.0',
+      registryEntryId: 1,
+      documentLoader,
+      typeTableLoader: () => typeTable
+    });
+
+    const decodedDocument = await decode({
+      cborldBytes,
+      documentLoader,
+      typeTableLoader: () => typeTable
+    });
+    expect(decodedDocument).to.eql(jsonldDocument);
+  });
+
+  it('should handle wide date range', async () => {
+    const CONTEXT = {
+      '@context': {
+        date: {
+          '@id': 'ex:date',
+          '@type': 'http://www.w3.org/2001/XMLSchema#date'
+        },
+      }
+    };
+    const jsonldDocument = {
+      '@context': CONTEXT['@context'],
+      date: [
+        '-1000-01-01',
+        '0-01-01',
+        '1000-01-01',
+        '1960-01-01',
+        '1960-01-01',
+        '1969-12-31',
+        '1970-01-01',
+        '1970-01-01',
+        '1970-12-31',
+        '2000-01-01',
+        '3000-01-01',
+        '10000-01-01'
+        // TODO: increase possible xsd:date value coverage
+      ]
+    };
+
+    const documentLoader = url => {
+      throw new Error(`Refused to load URL "${url}".`);
+    };
+
+    const typeTable = new Map(TYPE_TABLE);
+
+    const cborldBytes = await encode({
+      jsonldDocument,
+      format: 'cbor-ld-1.0',
+      registryEntryId: 1,
+      documentLoader,
+      typeTableLoader: () => typeTable
+    });
+
+    const decodedDocument = await decode({
+      cborldBytes,
+      documentLoader,
+      typeTableLoader: () => typeTable
+    });
+    expect(decodedDocument).to.eql(jsonldDocument);
+  });
+
   it('should revert remote type-scope', async () => {
     const CONTEXT_URL = 'urn:foo';
     const CONTEXT = {