Definitions for old style
Random House Webster's College Dictionary
Also, old′style`. a printing type style marked by more or less uniform thickness of all strokes and by slanted serifs.
(caps.) time reckoned according to the Julian calendar.
Origin of old style:
old style, old style font(noun)
a typeface (based on an 18th century design) distinguished by irregularity and slanted ascender serifs and little contrast between light and heavy strokes