- the old method of reckoning time according to the Julian calendar, which was off one day every 128 years
- [o- s-] an old style of type with narrow, light letters having slanted strokes at the top
Old Styleold style
- Printing A style of type originating in the 1700s 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.