http://www.arrl.org/160-meter

http://www.uska.ch/amateurfunkpraxis/wettbewerbe-und-diplome/schweizer-contest-kw/
2. Dezember 2017: SSB von 07:00 – 09:59 UTC
2. Dezember 2017: PSK31 von 10:00 – 10:59 UTC

http://www.procontestclub.ro/PCC%20Rules.html

http://www.uska.ch/amateurfunkpraxis/wettbewerbe-und-diplome/schweizer-contest-kw/
9 December 2017: CW from 07:00 – 09:59 UTC
9 December 2017: Digital from 10:00 – 10:59 UTC

http://raem.srr.ru/en/main/

http://www.agcw.org/index.php/en/contests-and-cw-activities/vhf-uhf-contest

http://www.arrl.org/rtty-roundup
The first full weekend of January, but never on January 1

http://www.eucw.org/eu160.html
The date is normally the first weekend of January each year except when the 1st January falls on the Saturday or Sunday . In such a case, the second weekend will be chosen.