p1 and p4 refer to std::chrono::duration which should just be chrono::duration.

p10 and p11 refer to sys_time which should be chrono::sys_time.

p12 is missing the chrono:: throughout:

equivalent to those formatted by a sys_­time initialized with clock_­cast<system_­clock>(t), or by a utc_­time initialized with clock_­cast<utc_­clock>(t)

p13 is says local_time which should be chrono::local_time

The declarations before p14 are a struct and a function in chrono whereas the surrounding definitions are all in namespace std. They should be shown as chrono::local-time-format-t and chrono::local_time_format(...).

p15 should refer to chrono::local-time-format-t

p17 should refer to chrono::sys_time.