After two teleconferences in the the High Court at Auckland this month, Justice Graham Lang issued a minute yesterday confirming the delay to trial.
He set a new date of June 2 next year for the four-week trial and said the move had come about "for a variety of reasons none of which are due to fault on the part of any counsel".
The rescheduling means the trial will now be ongoing during the anniversary of Mr Kumar's death.
Mr Kumar's son Shivneel said he had only heard of the rescheduling in the last couple of days and was very disappointed.
He did not want to comment further.
The victim's wife Anita was similarly too upset to discuss the delays.
A particularly early trial date was set because of the youth of the defendants, but Justice Lang said that was now "completely unrealistic".
"The Crown has also taken steps to ensure that its witnesses would be able to accommodate an early fixture. It is now clear, however, that counsel for the defendants will need to undertake significant further preparation prior to the trial," he said.
Defence lawyers Maria Pecotic and David Niven are seeking input from a variety of experts in relation to their clients and it is understood that would not have been available this month.
Both boys were denied bail at their first appearance in Waitakere Youth Court and the older defendant was again knocked back in September following a High Court bail hearing.
Since the tragedy the Kumar family had tried to sell the Railside Dairy but in August, with mounting bills, they were forced to reopen.
It is understood the business is yet to be sold.