Sometimes Thrulines is right sometimes way off.
One I saw the other day had parents for an ancestor born in Scotland c1788, so I was quite hopeful as lots of trees had them. The source was an Army record dated 1807 on the front, and since the recruit's age was 18 y 11 m, that looked good for our man.
Something nagged at me though, and I realised there were references to "Her Majesty". Of course in 1807 it would have been
His Majesty.
Looking through the pages of the record, it soon became clear that most of the dates in it were 20th century. He had signed on and done his 7 years plus 5 in the reserve. There was a second record where he'd gone back in 1919 and signed up to serve a year in the Labour Corps, presumably clearing the WWI battlefields.
I looked at the front again and saw that although the date
looked like 1807, it was actually
1897 and part of the 9 had disappeared. I've put in a correction so the indexed document date can be amended, but an awful lot of people have gone wrong already.