It was originally thought that Mark Bridger's appeal bid would be heard by leading judges at the Court of Appeal in London on January 24.
Bridger, a father of six, snatched April near her home in Machynlleth, Mid Wales, on 1st October 2012. Her body has never been found.
Sentencing Bridger in May, Mr Justice Griffith Williams said: "There is no doubt in my mind that you are a paedophile, who has for some time harboured sexual and morbid fantasies about young girls."
More top news
The significant development came after a forensic re-examination of a palm print left on a getaway vehicle.
Carla Lane was once one of the UK's highest paid screenwriters.
Politicians, royalty and the descendants of combatants in the Battle of Jutland commemorated the 8,648 seamen who died in the engagement.