DoB from age 76 in January 1859.

Source:  BB using Cemetery Records at UHF:
The Vow Cemetery
Erected by
Mary Jane and Lettitia Boyd
in memory of
their dear father John Boyd
who died 2nd Jan 9, 1859
aged 76 years
also their dear mother
Elisabeth Boyd
who died 14th Apr 1862
aged 77 years

DoD from his headstone at The Vow Graveyard.

Title:             
Forename:     Robert     
Surname:     Boyd     
Alt Surname:         
Date Of Death:     02/04/1867     
Date Of Grant:     26/04/1867     
Effects:     Effects under £100     
Registry:     Belfast     
Full Abstract:
The Will of Robert Boyd late of Maddikeel County Antrim Farmer deceased who died 2 April 1867 at same place was proved at Belfast by the oaths of William Young of Vow (Ballymoney) and James Boyd of Ballaghbiddy (Ballymoney) both in said County Farmers the Executors.

Pilot shows:
Name: Robert Boyde
Registration district: Ballymoney
Record type: DEATHS
Registration date - quarter and year: 1867
Estimated birth year: 1786
Age: 81
Mother's surnames:
Film number: 101583
Volume: 6
Page: 121
Digital GS number: 4200215
Image number: 00289
Collection: Ireland, Civil Registration Indexes 1845-1958
374; 2 Apr 1867, Maddykeel; Male; Widower; 81; Farmer; Exhaustion, No Medical Attendant; Hugh McCurdy, PAD, Vow.