ISO is the International Organization of Standards (abbreviating it to ISO instead of IOS appears to be for aesthetic reasons). It's an international organization which sets standards for a range of things.
ISO 8601 deals with how to write dates, a date format. Typically, in many parts of the world, you write the day then the month then the year and, principally in the US, in some places you write the month then the day then the year.
ISO 8601, however, specifies that you should write the year then the month then the day, ordering from most general to most specific. This is the way any date will be written by any ISO compliant organization so, despite this not being too common in lay usage, it appears in many contexts around the world.
No year is given on either of these locks, but months and dates are formatted to comply with ISO 8601 with the year part removed, hence the locks being compliant with a truncated ISO 8601.