If you spend any time reading 18th century literature, you’ll stumble upon some odd units of measure:

“Sennight” A space of seven days and nights, a week.   New Hampshire Gazette, April 27,1770: “..Advices from the Robbinhood (sic) Society. The last time I was at the club was on Tuesday sennight.”

“Ultimo” of or occurring in the month preceding the present.  “I called upon Miss Fairfax, on the 17th, ultimo”

“Twelvemonth” — a year.  “You will be waiting here a twelvemonth if you aren’t careful.”

“Fortnight” — a period of two weeks.   “Squire Allworthy remained confined to his bed for a fortnight.”