However the 12 months of a year are of some obscure mystic origin and have no real purpose today except that people are used to having them (they do not even describe the current position of the moon).
All of these alternatives can easily and automatically be distinguished from each other: The hyphens can be omitted if compactness of the representation is more important than human readability, for example as in In commercial and industrial applications (delivery times, production plans, etc.), especially in Europe, it is often required to refer to a week of a year.
Week 01 of a year is per definition the first week that has the Thursday in this year, which is equivalent to the week that contains the fourth day of January.
An abbreviated version of the year and week number like is sometimes useful as a compact code printed on a product that indicates when it has been manufactured.
Note: The ISO standard avoids explicitly stating the possible range of week numbers, but this can easily be deduced from the definition.
ISO 8601 should however be used to replace notations such as “2/4/95” and “9.30 p.m.”.