Both the UN and UNESCO are in the business of declaring calendar years by the Gregorian calendar to be the international year of this or that or the other. For example the UN has announced 2004 as the "International Year of Rice", while UNESCO has declared it to be the "International Year to Commemorate the Struggle against Slavery and its Abolition".

In reality, most people ignore these declarations, except for the purposes of trivia, and for where the declaration somehow relates to a particular interest or concern of theirs.

Of course, the UN has no monopoly on such declarations. For example, IUPAP has declared 2005 to be World Year of Physics. In fact, there is nothing stopping anyone from declaring any year to be anything they like, although they are likely to be totally ignored unless the organisation has some claims to importance (except of course by people whose interests are favoured by whatever declaration was made.)