fixes timestamping across timezones

lib/time_formatter.dart

@@ -1,4 +1,5 @@
 import 'package:intl/intl.dart';
+import 'package:timezone/timezone.dart' as tz;
 
 // Source - https://stackoverflow.com/a/54775297
 // Posted by diegoveloper, modified by community. See post 'Timeline' for change history
@@ -14,8 +15,11 @@ String _printDuration(Duration duration) {
 
 String formatTimeWindow(String? starts, String? ends) {
   if (starts != null && ends != null) {
-    DateTime startDt = DateTime.parse(starts);
-    DateTime endDt = DateTime.parse(ends);
+    DateTime? startDt = _tryParseServerDateTime(starts);
+    DateTime? endDt = _tryParseServerDateTime(ends);
+    if (startDt == null || endDt == null) {
+      return '--:--';
+    }
 
     Duration songLength = endDt.difference(startDt);
 
@@ -25,10 +29,108 @@ String formatTimeWindow(String? starts, String? ends) {
   return "--:--";
 }
 
-String formatStartingTime(String? startingTime) {
+String formatStartingTime(String? startingTime, {String? sourceTimezone}) {
   if (startingTime != null) {
-    DateTime dtStartTime = DateTime.parse(startingTime);
-    return DateFormat('jm').format(dtStartTime);
+    final DateTime? localStart = _serverTimeToLocal(
+      startingTime,
+      sourceTimezone: sourceTimezone,
+    );
+    if (localStart == null) {
+      return '--:--';
+    }
+    return DateFormat('jm').format(localStart);
   }
   return "--:--";
 }
+
+DateTime? _serverTimeToLocal(String rawTime, {String? sourceTimezone}) {
+  final DateTime? parsed = _tryParseServerDateTime(rawTime);
+  if (parsed == null) {
+    return null;
+  }
+
+  if (_hasExplicitTimezone(rawTime)) {
+    return parsed.toLocal();
+  }
+
+  // API timestamps are wall-clock values in the API timezone field.
+  if (sourceTimezone == null || sourceTimezone.trim().isEmpty) {
+    return parsed;
+  }
+
+  try {
+    final tz.Location sourceLocation = tz.getLocation(sourceTimezone.trim());
+    final tz.TZDateTime sourceTime = tz.TZDateTime(
+      sourceLocation,
+      parsed.year,
+      parsed.month,
+      parsed.day,
+      parsed.hour,
+      parsed.minute,
+      parsed.second,
+      parsed.millisecond,
+      parsed.microsecond,
+    );
+    return DateTime.fromMillisecondsSinceEpoch(
+      sourceTime.millisecondsSinceEpoch,
+      isUtc: true,
+    ).toLocal();
+  } catch (_) {
+    return parsed;
+  }
+}
+
+bool _hasExplicitTimezone(String value) {
+  final String trimmed = value.trim();
+
+  if (trimmed.endsWith('Z') || trimmed.endsWith('z')) {
+    return true;
+  }
+
+  final RegExp offsetPattern = RegExp(r'[+-]\d{2}:?\d{2}$');
+  return offsetPattern.hasMatch(trimmed);
+}
+
+DateTime? _tryParseServerDateTime(String value) {
+  final String trimmed = value.trim();
+  if (trimmed.isEmpty) {
+    return null;
+  }
+
+  final DateTime? isoAttempt = DateTime.tryParse(trimmed);
+  if (isoAttempt != null) {
+    return isoAttempt;
+  }
+
+  final RegExp serverDateTimePattern = RegExp(
+    r'^(\d{4})-(\d{2})-(\d{2})\s+(\d{2}):(\d{2}):(\d{2})(?:\.(\d{1,6}))?$',
+  );
+  final RegExpMatch? match = serverDateTimePattern.firstMatch(trimmed);
+  if (match == null) {
+    return null;
+  }
+
+  int parsePart(int group) => int.parse(match.group(group)!);
+
+  final int year = parsePart(1);
+  final int month = parsePart(2);
+  final int day = parsePart(3);
+  final int hour = parsePart(4);
+  final int minute = parsePart(5);
+  final int second = parsePart(6);
+
+  final String fraction = (match.group(7) ?? '').padRight(6, '0');
+  final int microseconds =
+      fraction.isEmpty ? 0 : int.parse(fraction.substring(0, 6));
+
+  return DateTime(
+    year,
+    month,
+    day,
+    hour,
+    minute,
+    second,
+    microseconds ~/ 1000,
+    microseconds % 1000,
+  );
+}