Mary Barrow - Birth

Does the document tell the year 1827 or does it only tell her age when married?
If only age you should remember that the year is just estimated based on the date for the event and it can fail with plus/minus one year depending if the real date is in the beginning or end of the year.

This is what I get for posting at 11pm! If she was born in 1827 she would be -younger- than if born in 1826 so it wasn't to make her older!

She was born in October and the wedding was in February. Maybe they provided her age at the time of the wedding, 15, (she -would be- 16 in October) and the clerk just assumed she was therefore born in 1827.

I would guess that when asked for your age it is only the age that is written in the original papers. When those papers are transliterated, for example by the LDS site familysearch they, for search purposes I assume, enters a year instead, very often with a result like this.