namespace std::chrono {
struct sys_info {
sys_seconds begin;
sys_seconds end;
seconds offset;
minutes save;
string abbrev;
};
}
A
sys_info object can be obtained
from the combination of a
time_zone and
either a
sys_time or
local_time.It can also be obtained from a
zoned_time,
which is effectively a pair of a
time_zone and
sys_time.[
Note 1:
This type provides a low-level interface to time zone information
.Typical conversions from
sys_time to
local_time
will use this class implicitly, not explicitly
. —
end note]
The
begin and
end data members indicate that,
for the associated
time_zone and
time_point,
the
offset and
abbrev are in effect in the range [
begin, end)
.This information can be used to efficiently iterate the transitions of a
time_zone.The
offset data member indicates
the UTC offset in effect
for the associated
time_zone and
time_point.The relationship between local_time and sys_time is:
offset = local_time - sys_time
The
save data member is extra information not normally needed
for conversion between
local_time and
sys_time.If
save != 0min, this
sys_info is said to be on “daylight saving” time,
and
offset - save suggests what offset this
time_zone might use
if it were off daylight saving time
.However, this information should not be taken as authoritative
.The only sure way to get such information
is to query the
time_zone with a
time_point
that returns a
sys_info where
save == 0min.There is no guarantee what
time_point might return such a
sys_info
except that it is guaranteed not to be in the range [
begin, end)
(if
save != 0min for this
sys_info)
.The
abbrev data member indicates
the current abbreviation used for the associated
time_zone and
time_point.Abbreviations are not unique among the
time_zones,
and so one cannot reliably map abbreviations back to a
time_zone and UTC offset
.template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, const sys_info& r);
Effects: Streams out the
sys_info object
r in an unspecified format
.