DateTime.ToString() format that can be used in a filename or extension?

Question

I want to add a timestamp to filenames as files are created but most of the DateTime methods I\'ve tried output something with spaces and slashes. For instance:

Answer 1

Personally I like it this way:

DateTime.Now.ToString("yyyy-MM-dd HH.mm.ss")

Because it distinguishes between the date and the time.

Answer 2

I would use the ISO 8601 format, without separators:

DateTime.Now.ToString("yyyyMMddTHHmmss")