Speedboat killer Jack Shepherd has had 78 days cut from his 10-year jail term because of time he served waiting for extradition after fleeing the UK to Georgia.
Three appeal judges said the 78 days Shepherd spent in custody awaiting extradition in Georgia should count as part of the jail term he is serving.
Shepherd, 32, was given a six-year sentence after being convicted of manslaughter by gross negligence following the death of Charlotte Brown when his speedboat capsized during a champagne-fuelled date on the River Thames in 2015.
Speedboat killer Jack Shepherd should leave prison sooner than expected as a result of a ruling by Court of Appeal judges. Shephered, 32, was extradited from Georgia after a trial in his absence found him guilty of the manslaughter of Charlotte Brown
Charlotte Brown, 24, was killed after Shepherd's boat capsized on the Thames near Wandsworth Bridge in 2015
Ms Brown, from Clacton, Essex was on her first date with Shepherd after meeting on dating website OkCupid.
Shepherd's trial in July 2018 heard how he had bought the 1980s boat on Gumtree and had tried to impress other women with it.
But his first date with Ms Brown ended in tragedy when the 14ft Fletcher Arrowflyte GTO, which was riddled with defects, hit a log and capsized, throwing them into the river near Wandsworth Bridge.
He later sparked outrage by launching an appeal against the conviction while on the run in Georgia - and he was awarded funds to do so.
After spending ten months on the run, Shepherd was finally extradited and ordered to serve six years with six months consecutive for skipping his bail in April last year.
The web designer then admitted hitting a barman over the head with a vodka bottle in a hotel in Devon and was given four years extra.
Jack Shepherd was jailed for six years for manslaughter by negligence, he was sentenced to a further four years after admitting wounding a barman
Three appeal judges said on Thursday that the time Shepherd spent awaiting extradition should count towards his time served.
He did not attend the five minute hearing as Lord Justice Fulford, sitting with Mr Justice Holgate and Sir Roderick Evans, said: We agree the application should be granted.'
Jurors had heard how Shepherd used the speedboat as part of his 'seduction routine' and he may have taken up to ten women on a boozy cruise.
After meeting online, Shepherd and Ms Brown shared two bottles of wine over dinner at The Oblix restaurant in The Shard.
He invited her back to his Hammersmith houseboat where they had more drinks and then out for a high-speed champagne sightseeing tour in his red speedboat.
The speedboat owned by web designer Jack Shepherd, which crashed in the Thames in 2015
Ms Brown can be heard yelling: 'Oh my God, you're going so fast' as she made a video on their way up to the Houses of Parliament.
But the encounter went horribly wrong when Shepherd decided to hand the wheel to Ms Brown.
The speedboat capsized opposite Plantation Wharf, near Wandsworth Bridge and Shepherd was found clinging to upturned bow of the boat.
Witnesses described hearing him shouting out 'Help me', rather than 'Help us'.
He was unsteady on his feet and still reeked of alcohol after lifeguards hauled him from the river.
Charlotte was found dead or dying when she was pulled out of the icy water after a frantic search.
When the married father-of-one was hauled back from Georgia he appeared at the Old Bailey and admitted skipping bail.
He had two months taken off his sentence for pleading guilty - meaning he was handed just six months, on top of his six year manslaughter sentence.
However, this decision was overturned after his lawyers argued the Old Bailey did not have the proper 'jurisdiction' to convict him on the bail offence.
Last year Charlotte's family started to campaign for a law that brings in tighter controls on buying and driving boats.
Shepherd's trial revealed that anyone can hire a boat for personal use without training or a licence, while it was also not mandatory to wear or carry a life jacket.
Speaking on ITV's Lorraine last October, her mother Roz Wicken: 'If I could take her place in the blink of an eye, I would have done… We miss Charlotte so dreadfully.
Her sister, Katie Brown, added: '(Charlotte) was so funny and loving, she was passionate, do anything for her friends and family. Life isn't the same without her.
'But we need to let her legacy live on and make a change, so that hopefully this would be much less likely to happen if those laws were in place.'