After the 52,763rd ticket for the event was sold this morning, it means the four teams are guaranteed to play in front of a record Guinness PRO12 crowd.
The previous attendance record had been set at last year's Judgement Day, and it follows hot on the heels of Leinster and Munster's clash earlier this month - which attracted 43,108 fans to the Aviva Stadium.
Commenting on the record-breaking crowd, Martin Anayi, managing director, Guinness PRO12 Rugby said:
"Judgement Day has become one of the Guinness PRO12's 'must-go-to' events and it is terrific news that with three weeks to go until the event the previous attendance record has been broken.
"With over 28,000 recently attending the Guinness PRO12 derbies in Wales; over 43,000 flocking to Dublin's Aviva Stadium for Leinster against Munster; and the climax to the season, the Guinness PRO12 Final at BT Murrayfield on 28 May, already on course to be one of the biggest finals ever; it shows there is a huge appetite and opportunity for fans to be part of some great Guinness PRO12 occasions over the last two months of the season."
The Blues and Ospreys are both still vying for a play-off spot in the Guinness PRO12 this season, currently lying 10 and 14 points, respectively, behind the fourth placed Scarlets - with 15 points from three bonus point wins still theoretically available.
The all-important top six spots in the table - which would at present reading bring qualification for the 2016/2017 European Champions Cup - are also within touching distance for each side, as they are currently lying in eighth and ninth places.
The Dragons are mathematically out of play-off contention and can't finish in the top seven, but a strong run in Europe is keeping their season alive in style - they face Montpellier in the European Challenge Cup semi-finals the week preceding JDIV.
Therefore, all four Welsh regions have a lot to play for heading into the business end of the season, ensuring this year's Judgement Day is set to be a spectacular one.
"Last year's Judgement Day fixtures saw us process thousands of tickets on the day of the event and we fully expect a large walk-up crowd at Principality Stadium for another guaranteed record breaking day this year," said a WRU spokesperson.
"It will be a proud moment when during the second match of the day we announce our final crowd figure and set another new record for attendance at a Guinness PRO12 match-day.
"But, whilst it is great news for us at the turnstiles that we get so many last minute purchasers for this celebration of regional rugby, we would like to remind people that buying tickets in advance is the best way to ensure they get the seats they want and don't miss out on any of the action."
Tickets for Judgement Day IV have been frozen at 2015 prices and can be purchased now at £10 per person (booking fees apply) from www.wru.wales/tickets (print at home available), by calling 0844 847 1881, in person from the WRU Ticket Office on Westgate Street, from each of the four regions or from Tesco stores throughout Wales.
Season tickets purchased from either of the home teams - Blues and Dragons - include access to Judgement Day IV, with fans asked to liaise with the respective box offices.
Both matches will be shown live on television with BBC Wales showing the first match and S4C the second.
63x46.png){kind=logo}