Donnie Snook told provincial court in Saint John he was sorrowful for the crimes, which police said involved one boy.
"I have deep sadness for the darkness I have created for so many people," Snook said Tuesday.
"It's too late to change the things I've done."
Snook, 41, pleaded guilty last month to two counts each of sexual assault and sexual interference.
The Crown withdrew one count of sexual interference after a review of the case determined the victim was 15 at the time of the offence. The age of consent at that time was 14.
He pleaded guilty to the charges after they were transferred to New Brunswick provincial court from Newfoundland.
Police said the offences occurred between Dec. 1, 1995, and August of 1996 at or near Mount Moriah, N.L., and at or near Barachois Pond Provincial Park while Snook was working with the Salvation Army.
Judge Alfred Brien said he took into account a number of factors before issuing his sentencing decision, including the fact that Snook volunteered information to the police, he had no criminal record prior to the offences and the law as it was at the time of the crimes.
"Any assault on a young person is a serious matter," Brien said.
Defence lawyer Dennis Boyle said the extra three months was appropriate.
He said now, Snook can begin to put his past behind him.
"It's a new start for him and he can work his way through a lot of things," Boyle said outside the court.
Snook was sentenced in September to 18 years in prison after pleading guilty to 46 charges including sexual assault and possessing, distributing and making child pornography over a 12-year period.
He is appealing that sentence, arguing it is unreasonable and in excess of the appropriate range.
The Crown is also appealing, saying the trial judge in that case gave Snook too much credit for time served in pre-trial custody.
Snook was given 1 1/2 credit for time served, reducing his sentence to 16 years and 10 months, and he would be eligible for parole after serving one-third of that.
Crown prosecutor Karen Lee Lamrock also says the judge failed to consider a section of the Criminal Code that would require an offender to serve half their sentence or 10 years, whichever is less, before becoming eligible for parole.