He is listed as 4 in 1881 - Baptism 21 July 1877
Find a grave - if he died in Southampton 19 Jun 1947 - has birth 1 Apr 1876
The 1881 census was on April 3rd, so if that is correct one might suppose the parents had just celebrated a birthday

But a gravestone is quite likely to be a year out, when people were commonly referred to as 'in their 82nd year' meaning they were actually 81.
I have found someone in the 1939 Register born on 1 October 1880, while the birth had been registered on that day in 1878. People usually remembered their birthday but had very occasional need to know which year it was in !