timeAgo method
Returns a human-readable "time ago" string.
Implementation
String timeAgo() {
final now = DateTime.now();
final difference = now.difference(this);
if (difference.inDays > 1) return '${difference.inDays} days ago';
if (difference.inHours > 1) return '${difference.inHours} hours ago';
if (difference.inMinutes > 1) return '${difference.inMinutes} minutes ago';
return 'just now';
}