Denis Killeen was born about 1786 in the parish of Meelick in East Galway. On 10 December 1804 (presumably at the age of eighteen), he enlisted in the 97th Regiment of Foot (at “Clonaney” [Clonony?], King’s County [County Offaly]).
From the record of his discharge (10 December 1818), a physical (and occupational) description:
To prevent any improper use being made of this Discharge, by its falling into other Hands, the following is a Description of the said Denis Killeen. He is about thirty two Years of Age, is five Feet ten Inches in height, fair Hair, Grey Eyes, Swarthy Complexion; and by Trade or Occupation a Carpenter.1
Note the imprecision of “about ____ Years of Age,” in an official service record for a private in His Majesty’s 97th Regt of Foot.
Nowadays, an official military record (or an official record of any sort) will give a precise age, with an exact date of birth. For that matter, nowadays even most unofficial records will supply exact birth dates, based on the stringent demands for accuracy that define contemporary record-keeping: try sending your kid to sleepaway camp without providing the exact day/month/year of the child’s birth on the registration form! But two hundred years ago, people (the common folk, that is, but that was most people…) were a quite a bit looser about birth dates (which is one reason why, when searching 19th-century census returns, you should generally treat recorded birth years as rough estimates, perhaps accurate to within plus or minus five years or so of the given date).
Denis Killeen was discharged due to the disbandment of his regiment, after having served 14 years and 1 day. He received a pension from the Crown on 26 August 1819 (at which point he was in Upper Canada). On 26 May 1828 he received a patent from the Crown for one hundred acres, at the south half of Lot 11, Third Concession, in the township of March (Carleton Co., Ontario).
1 The National Archives of the UK (TNA), WO 119/70, Kilmainham Ref: [None] (Index No = 16), folio 43.