Guernsey's Royal Court heard that Pinsard was born in 1919 and claimed he had endured years sexual abuse at the Haut de la Garenne children's home.
The Jersey home came under intense scrutiny in 2008 after police took statements from 192 alleged victims of historic child abuse.
Pinsard joined the army after leaving Haut de La Garenne, where he realised his sexual outlook and experiences were different to other peoples.
The court heard he later indecently assaulted the two young girls through curiosity and naivety.
The abuse began in 1951, and the court was told the victims did not report what was happening because they were too young to understand what was happening and that they trusted Mr Pinsard.
He was first questioned by Guernsey Police officers last year and immediately confessed to carrying out the abuse over a nine year period.
The court heard how Pinsard touched the first girl on numerous occasions between 1951 and 1955, and the second between 1964 and 1969 at his home in St Sampson, Guernsey.
In a statement read out in court Mr Pinsard admitted he felt ashamed and knew at the time what he was doing was wrong but he could not control it.
Pinsard was married with four children at the time of the offences, which took place over a period of nine years and only stopped when he decided to "stop his filthy habit".
He explained to the court how he 'didn't want to hurt any children'.
His wife has now passed away, but Pinsard was accompanied to court by his son.
At an earlier hearing the defendant, who uses a hearing aid, admitted nine charges of indecent assault.
Pinsard's defence asked the court to exercise extreme caution, suggesting it would be difficult for the prison to accommodate his needs and medication.
In sentencing, Judge Russell Finch acknowledged it was "a difficult situation" and took his age and health into account, stating that a younger man would have received between seven and nine years.
Accounting for the risk of the defendant becoming ill and dying in Prison, Mr Finch sentenced Pinsard to two 18-month sentences in Les Nicolles prison, which will run concurrently.
The Prison Officers Association have said they believed Pinsard is the oldest serving prisoner in the British Isles.
