Handle dates from before the epoch.

Author: dlongley

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

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} = {}) {

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} = {}) {

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 = _getNumberTokenType(secondsSinceEpoch);
+    const secondsToken = new Token(tokenType, secondsSinceEpoch);
     const millisecondIndex = value.indexOf('.');
     if(millisecondIndex === -1) {
       const expectedDate = new Date(
@@ -38,7 +39,7 @@ export class XsdDateTimeEncoder extends CborldEncoder {
     // compress with subsecond precision
     const entries = [
       secondsToken,
-      new Token(Type.uint, milliseconds)
+      new Token(_getNumberTokenType(milliseconds), milliseconds)
     ];
     return [new Token(Type.array, entries.length), entries];
   }
@@ -56,3 +57,7 @@ export class XsdDateTimeEncoder extends CborldEncoder {
     return new XsdDateTimeEncoder({value, parsed});
   }
 }
+
+function _getNumberTokenType(number) {
+  return number >= 0 ? Type.uint : Type.negint;
+}