He assumed duties on 22 August and reached 55 years of age on 26 September.
The tenure given him expires on 26 October.
All his predecessors since 1973 had remained in the job for at least one year, with the most immediate Ravindra Wijegunawardena having had a two year and one month term courtesy three extensions.
Commendations to turn to displeasure
The president was commended, both locally and internationally, for appointing Sinniah as the Navy chief.
That will turn to disapproval if his term is confined to just two months.
According to reports reaching Sri Lanka Mirror, a top official in the defence ministry wants to send Sinniah on retirement immediately, so that he could be succeeded by an officer from Ambalangoda, which is his hometown too.
The Navy officer from Ambalangoda is backed by minister Sarath Fonseka as well, as the latter too, is from the same town.
As reported by SLM previously, Sinniah is without an official residence and official vehicle.