If you wish to have a deterministic format, but do not want to use a specific culture, you can use InvariantCulture.
InvariantCulture represents no culture at all – it is associated with the English language, though no specific country/region.
See Using the InvariantCulture Property on MSDN.
Here is an example of its use:
DateTime dt = new DateTime(2011, 11, 21, 12, 34, 56); Console.WriteLine(dt.ToString(CultureInfo.InvariantCulture));