Every 1st Tuesday of the new year is Disclosure Day (Openbaarheidsdag) in the Netherlands, the day when the National Archive opens up material and collections whose access restrictions have expired. It is generally a day approached with a sense of festivity by archivists (openness is their core public service and they’re also eager to show what cool stuff they have on record), and the hashtag #openbaarheidsdag shows a variety of tweets. Next to the National Archive, a range of local and regional archives participate, amongst which is the Frisian regional archive Tresoar. With both institutions I had the pleasure of working together last year (related to openness but unrelated to disclosure day). There is some momentum building to turn it into a nationally observed day by all archives, to celebrate the work and value of archives.

Photo of the National Archive building next to The Hague Central Station, by 23Archiefdingen CC BY-SA
In general the material opened up for the general public on a Disclosure Day wasn’t fully secret, but access was restricted to e.g. researchers. Some of it, such as personal correspondence and material from private archives however hasn’t been seen by anyone for multiple decades. Various time limits apply. Government documents are transferred to the National Archive after 20 years and most of it will be publicly accessible then right away (before that transfer the relevant Ministry itself determines openness, and freedom of information regulations apply). Where things like the privacy of living persons or national security are involved access can be restricted for a maximum of 75 years. That limit is set at the start, and per the first January after that limit expires, it becomes public. So for this year, it means that 1997 (20 yrs), 1967 (50 yrs) and 1942 (75 yrs) are the years for which new material is being published (as 50 and 75 years are commonly used time limits on access, and 20 yrs the legal default).
The amount of material published each year is substantial. Just the index of material published this year by the National Archives is over 1200 pages, and only the table of contents of that index of material is already 50 pages.

Lots of manual work involved, such as this tweet by National Archive employee Maartje v.d. Kamp illustrates. She says “green dots mark restricted access, disclosure day means scraping lots of dots from archive boxes”
For this year the collection of newly accessible material contains the minutes of Cabinet meetings of the mid 1990’s (in which the Prime Minister berates his Ministers for leaking and carelessly letting opinions be publicly known), the personal notes of the researcher who on behalf of the government looked into the riots during the 1966 wedding of future Queen Beatrix, as well as personal notes from the same researcher when looking into the war history of a government minister alleged to have served in the SS. These haven’t been opened at all, since then, and the National Archive itself wondered what is in it that made the researcher claim years of secrecy for it. Also the diaries of the first woman Minister in the Netherlands and a prime minister in the late 1940’s became public.
Of special interest this year is the disclosure of the Dutch Trustfund (Nationaal Beheersinstituut) that between 1945 and 1967 managed all the Dutch funds and assets seized from German nationals after the war and from Dutch (suspected) collaborators and profiteers until after their court verdicts, as well as funds and assets of missing persons (such as jewish people deported by the nazis during the war, or in hiding and not yet returned) until their fate was known. The index of all persons for whom assets were managed, or from whom assets were seized, contains some 180.000 names, and is available online. The Dutch Trustfund archive itself hasn’t been digitised yet (as it wasn’t public yet), and stretches 2.5km of shelves.
Out of curiosity I did a quick search to look for my grandparents but none of them show up in the index. So there wasn’t some never shared family secret. 😉

E.J. Voute, collaborating mayor of Amsterdam during the nazi occupation on the photo above (source Spaarnestad archive, within the National Archive. Photo taken during his trial, 25 April 1947), and the location in the list of the Dutch Trustfund archives where he’s mentioned.