How to add timestamp (date) to BenchmarkDotNet exported HTML or CSV file names?

There is an option for that (Config Options doc):

ConfigOptions.DontOverwriteResults - The exported result files should not be overwritten (by default they are overwritten).

So try adding:

WithOptions(ConfigOptions.DontOverwriteResults);

Alternatively you can use fileNameSuffix.

Some of the standard exporters already allow passing fileNameSuffix, for example - XML and Json one:

AddExporter(JsonExporter.Custom("customFileNameSuffix", indentJson: true, excludeMeasurements: true));

public class MyHtmlExporter : HtmlExporter
{
    public MyHtmlExporter()
    {
        FileNameSuffix = $"gurustron{DateTime.UtcNow.Ticks}";
    }
    protected override string FileNameSuffix { get; }
}

AddExporter(new MyHtmlExporter());

public class MyCsvExporter : CsvExporter
{
    public MyCsvExporter() : base(CsvSeparator.CurrentCulture) // mimic the Default behavior
    {
        FileNameSuffix = $"gurustron_{DateTime.UtcNow.Ticks}";
    }
    protected override string FileNameSuffix { get; }
}

One thing I noticed - not all suffixes actually work, for example DateTime.UtcNow.ToLongTimeString() (instead of DateTime.UtcNow.Ticks) has not worked for me.