There were four John Clegg's baptised in 1812:
Baptism: 16 Feb 1812 St Chad, Rochdale, Lancashire, England
John Clegg - Son of James Clegg & Hannah, his wife
Abode: Parade St.
Occupation: Weaver
Source: LDS Film 2356442/3 and 1545791
Baptism: 30 Aug 1812 St Chad, Rochdale, Lancashire, England
John Clegg - Son of James Clegg & Nancy, his wife
Abode: Oakenrod
Occupation: Labr.
Source: LDS Film 2356442/3 and 1545791
Baptism: 8 Nov 1812 St Chad, Rochdale, Lancashire, England
John Clegg - Son of John Clegg & Ann, his wife
Abode: Blackwater St.
Occupation: Clogger
Source: LDS Film 2356442/3 and 1545791
Baptism: 27 Dec 1812 St Chad, Rochdale, Lancashire, England
John Clegg - Son of Horsefall Clegg & Mary, his wife
Abode: Coal Pit Lane
Occupation: Weaver
Source: LDS Film 2356442/3 and 1545791
Many more a year or two either side.