https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114279
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- It certainly does take leap seconds into account, as demonstrated by the output example below the text you quoted, which is reproduced in the testsuite: https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libstdc%2B%2B-v3/testsuite/std/time/clock/utc/io.cc;h=55c53dc4057fe90b8a0f7192cc38ffe313f5afd4;hb=HEAD And also: https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libstdc%2B%2B-v3/testsuite/std/time/clock/utc/leap_second_info.cc;h=2fabda494234a48dc2920e291f5a92a8fe1d02fa;hb=HEAD This seems to be just a bug in the from_stream overload, not utc_clock.
