Please take this as your official notice that you use dates completely wrong and the world thinks you are a terrible person. If you would like to be a good person, please correct your horrific use of dates immediately
Medium/Small/Big Big:Medium:Small - No! Bad American!
Big-Medium-Small Big:Medium:Small—Yes! You're now ISO 8601 compliant!
ISO 8601 is a great standard when you need interoperability (e.g. between machines/servers, or between humans in different locales) or the ability to sort by timestamp.
For personal note taking, or notes to be shared locally, it makes sense to use your local locale's format.