Print logging information to VS Output window on Diagnostic mode

If Diagnostic mode is on, stack traces are dumped into VS Output window (F# Power Tools tab). Any idea in order to make logging information more descriptive is welcome.
You can write 

```fsharp
 String.Format("[VFPT][{0} {1:hh:mm:ss tt}] {2}{3}",
                logType.ToString(), DateTime.Now, message, Environment.NewLine)
```

However, I'm not sure `tt` is a valid placeholder.