UPDATE 23 September: with about 4 days to go Geenstijl reports 255 000 out of 300 000 referendum requests have been received; which still means -if the data are correct- it will a close call whether NL will organise a referendum on the Association Agreement...
UPDATE 8 September: About halfway in the 6 week period available to obtain the necessary 300 000 signatures, 140 000 (47%) have been obtained. It seems to becoming a close call, whether a referendum will need to be called.
The UK will have its in-or-out referendum in 2016 and Denmark organizes in December an opt-out to opt-in referendum: changing their default opt out in civil and justice matters to an opt in. In this way they can, like the UK and Ireland, decide regulation by regulation whether to participate or not.
Also for the Netherlands an EU-related referendum might be in the works. IF it happens, its timing will be interesting: in the first quarter of 2016 and during the Dutch EU presidency.
A possible Dutch EU referendum is however not an in-or-out referendum, but addresses a less immediate topic: the association agreement the EU (and its 28 member states) concluded with Ukraine last year. Approval of the Agreement is running smoothly, with ratification of Ukraine, 22 EU states as well as the European parliament already fully finished. The Netherlands have finished their parliamentary process resulting in publication of the approval act on 28 July 2015. If it had been approved 1 month earlier, that would be the formal end of the democratic process and the Netherlands could proceed to deposit its instrument of ratification with the Council of the European Union. But on 1 July quietly the "Wet raadgevend referendum" (WRR, "Consultational" Referendum Act; translation as "Advisory Referendum Act" is also possible, but note it only advises after an act has been signed into law) came into force, giving groups of people the possibility to call a referendum.
Ukraine Association agreement
The request for a referendum is a two-stage process: first 10 000 signatures for a "preliminary request" have to submitted to the Dutch Election Council (Kiesraad) within 4 of the publication. After that stage is succesful, 300 000 applications for a referendum have to be raised within 6 weeks.
The first act to pass the preliminary stage was the Ukraine-EU Association Agreement approval act, after a campaign by website geenstijl.nl (via geenpeil.nl) and burgercomite-eu.nl/. This means the approval act is now suspended until the Kiesraad has announced wether sufficient applications for the referendum have been raised. The deadline for submission of applications is 28 September.