Invalid datetime data formatting in CSV data source connected to a PostgreSQL database with .NET

Hello,
There is an issue with CSV data source connected to a PostgreSQL database with .NET.

After upgrading the Npgsql package from 4.1.8 to 5.0.3 the data for datetime columns are returned in invalid format.
Before package upgrade the data was looking like this:
d+CreationTime,t+TimeSpent
2021-01-29T17:41:32Z,60
2021-02-02T12:12:19Z,2700
After upgrading the data formatting is broken
+CreationTime,+TimeSpent
"1/29/2021 5:41:32 PM","00:01:00"
"2/2/2021 12:12:19 PM","00:45:00"

Data retrieved from database with code:

// ....
using (IDataReader dataReader = await command.ExecuteReaderAsync())
{
    using (Stream inputStream = Compressor.Compressor.CompressDb((DbDataReader)dataReader))
    {
        using (StreamReader streamReader = new StreamReader(inputStream))
        {
            return await streamReader.ReadToEndAsync();
        }
    }
}

How the issue can be solved?

Thanks for your help.