LongtoDateConverter.cs

using System.Globalization;

namespace MauiWeatherForecast
{
    public class LongToDateConverter : IValueConverter
    {
        DateTime _time = new DateTime(1970, 1, 1, 0, 0, 0, 0);
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            long dateTime = (long)value;
            return $"{_time.AddSeconds(dateTime).ToString()} UTC";
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}