A leap year starting on Friday is any year with 366 days (i.e. it includes 29 February) that begins on Friday, 1 January, and ends on Saturday, 31 December. Its dominical letter hence is CB, such as the years 1932, 1960, 1988, 2016, 2044, 2072, and 2112 in the Gregorian calendar or, likewise, 2000 and 2028 in the obsolete Julian calendar.
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Gregorian Calendar
Leap years starting on a Friday, along with leap years that start on Sunday, occur most frequently of all the leap years (15 times out of the 97 total leap years) in a 400-year cycle (20871 weeks) in the Gregorian calendar. Thus, the overall frequency is 3.75% (15 out of 400) or approximately 15.5% (15 out of 97) if just leap years are taken into consideration.
Julian Calendar
Like all leap year types, the one starting with 1 January on a Friday occurs exactly once in a 28-year cycle in the Julian calendar, i.e. in 3.57% of years.
The final two digits of Julian years repeat after 700 years, i.e. 25 cycles.