The 28MHz SWL Contest will be in the second full weekend of December, so this year on 12 and 13 December. This is the same weekend of the ARRL 10Meter Contest.
For the rules you may visit the website of the VERON, SWL section: https://www.veron.nl/vereniging/commissies-en-werkgroepen/nl-commissie/swl-contesten-nlc/ .
Wishing you lots of success in this and other contests!
73, Ruud Ivens, NL290, SWL Contest Manager VERON.