id summary reporter owner description type status milestone component version severity resolution keywords cc 9146 chrono_io support for time format with fractional seconds Johan Lundberg viboes " I propose %f and %F is added to chrono_io in analogy with http://www.boost.org/doc/libs/1_53_0/doc/html/date_time/date_time_io.html Unfortunately this is just a specification, no suggested implementation. Examples: {{{ 1970-01-01 00:02:46 1970-01-01 00:02:46.7 1970-01-01 00:02:46.67 1970-01-01 00:02:46.667 }}} all the way up to nanoseconds (as gnu date +%N): {{{ 1970-01-01 00:02:46.666666667 }}} (variants with T instead of space, and time-zone are the real use-cases, but that aspect already works) Some tools write fractional seconds only if they are not zero. date_time_io supports that using %F so I suggest that for chrono_io as well. To support writing all of the above formats one could allow for example %3f (and %3F) for printing .667. Alternatively, %N for nanoseconds. When parsing i suggest the number of digits specified is ignored but I may be wrong on that. In addition to the above, the documentation has no list of allowed keys for the format strings. references: * The bug https://svn.boost.org/trac/boost/ticket/7868 was just fixed. * doc: http://www.boost.org/doc/libs/1_54_0/doc/html/chrono/users_guide.html#chrono.users_guide.getting_started.hello_world__ : 'Unfortunately there are no formatting/parsing sequences which indicate fractional seconds. Boost.Chrono does not provide such sequences. In the meantime, one can format and parse fractional seconds for system_clock::time_point by defaulting the format, or by using an empty string in time_fmt().' " Feature Requests closed Boost 1.55.0 chrono Boost 1.54.0 Problem fixed