- the old method of reckoning time according to the Julian calendar, which was off one day every 128 years
- an old style of type with narrow, light letters having slanted strokes at the top
See Old Style in American Heritage Dictionary 4
- Printing A style of type originating in the 18th century and characterized by slight contrast between light and heavy strokes and slanting serifs.
- Old Style Abbr. OS or O/S The method of reckoning dates according to the Julian calendar.