fix reading and writing of modification time.

lib/src/kdbx_meta.dart

@@ -14,6 +14,10 @@ import 'package:quiver/iterables.dart';
 import 'package:xml/xml.dart' as xml;
 import 'package:xml/xml.dart';
 
+import 'package:logging/logging.dart';
+
+final _logger = Logger('kdbx_meta');
+
 class KdbxMeta extends KdbxNode implements KdbxNodeContext {
   KdbxMeta.create({
     @required String databaseName,
@@ -182,8 +186,9 @@ class KdbxMeta extends KdbxNode implements KdbxNodeContext {
       defaultUserNameChanged.set(other.defaultUserNameChanged.get());
     }
     if (other.masterKeyChanged.isAfter(masterKeyChanged)) {
-      throw UnimplementedError(
+      // throw UnimplementedError(
-          'Other database changed master key. not supported.');
+      //     'Other database changed master key. not supported.');
+      _logger.shout('MasterKey was changed? We will not merge this (yet).');
     }
     if (other.recycleBinChanged.isAfter(recycleBinChanged)) {
       recycleBinEnabled.set(other.recycleBinEnabled.get());

lib/src/kdbx_times.dart

@@ -23,9 +23,10 @@ class KdbxTimes extends KdbxNode implements KdbxNodeContext {
 
   DateTimeUtcNode get creationTime => DateTimeUtcNode(this, 'CreationTime');
   DateTimeUtcNode get lastModificationTime =>
-      DateTimeUtcNode(this, 'CreationTime');
+      DateTimeUtcNode(this, 'LastModificationTime',
-  DateTimeUtcNode get lastAccessTime => DateTimeUtcNode(this, 'CreationTime');
+          defaultValue: () => creationTime.get() ?? DateTimeUtcNode.minDate);
-  DateTimeUtcNode get expiryTime => DateTimeUtcNode(this, 'CreationTime');
+  DateTimeUtcNode get lastAccessTime => DateTimeUtcNode(this, 'LastAccessTime');
+  DateTimeUtcNode get expiryTime => DateTimeUtcNode(this, 'ExpiryTime');
   BooleanNode get expires => BooleanNode(this, 'Expires');
   IntNode get usageCount => IntNode(this, 'UsageCount');
   DateTimeUtcNode get locationChanged =>

lib/src/kdbx_xml.dart

@@ -231,13 +231,17 @@ class BooleanNode extends KdbxSubTextNode<bool> {
 }
 
 class DateTimeUtcNode extends KdbxSubTextNode<DateTime> {
-  DateTimeUtcNode(KdbxNodeContext node, String name) : super(node, name);
+  DateTimeUtcNode(KdbxNodeContext node, String name, {this.defaultValue})
+      : super(node, name);
 
   static const EpochSeconds = 62135596800;
+  final DateTime Function() defaultValue;
 
   KdbxReadWriteContext get _ctx => (node as KdbxNodeContext).ctx;
+  static final minDate = DateTime.fromMillisecondsSinceEpoch(0, isUtc: true);
 
-  bool isAfter(DateTimeUtcNode other) => get().isAfter(other.get());
+  bool isAfter(DateTimeUtcNode other) =>
+      (get() ?? minDate).isAfter(other.get() ?? minDate);
 
   void setToNow() {
     set(clock.now().toUtc());
@@ -246,7 +250,7 @@ class DateTimeUtcNode extends KdbxSubTextNode<DateTime> {
   @override
   DateTime decode(String value) {
     if (value == null) {
-      return null;
+      return defaultValue?.call();
     }
     if (value.contains(':')) {
       return DateTime.parse(value);