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Model the TAI-UTC difference between 1961 and 1972

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Howard Hinnant
2018-10-03 17:51:55 -04:00
parent 591f572b67
commit 1eed461d06
2 changed files with 102 additions and 3 deletions
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103
include/date/tz.h
View File

@ -2057,6 +2057,73 @@ template <class Duration>
using tai_seconds = tai_time<std::chrono::seconds>;
namespace detail
{
template <class Duration>
inline
std::chrono::duration<long double, days::period>
mjd(sys_time<Duration> tp)
{
using namespace std::chrono;
// constexpr auto off = sys_days{1970_y/1/1} - (sys_days{-4713_y/11/24} + hours{12}) -
// dday{2400000.5};
constexpr days off{40587};
return tp.time_since_epoch() + off;
}
template <class Duration>
Duration
pre_leap(sys_time<Duration> tp)
{
using namespace std::chrono;
using dsec = duration<long double>;
if (tp >= sys_days(1972_y/January/1))
return seconds{10};
if (tp < sys_days(1961_y/January/1))
return Duration{0};
if (tp < sys_days(1961_y/August/1))
return duration_cast<Duration>(
dsec{1.422818} + (mjd(tp) - days{37300}).count() * dsec{0.001296});
if (tp < sys_days(1962_y/January/1))
return duration_cast<Duration>(
dsec{1.372818} + (mjd(tp) - days{37300}).count() * dsec{0.001296});
if (tp < sys_days(1963_y/November/1))
return duration_cast<Duration>(
dsec{1.845858} + (mjd(tp) - days{37665}).count() * dsec{0.0011232});
if (tp < sys_days(1964_y/January/1))
return duration_cast<Duration>(
dsec{1.945858} + (mjd(tp) - days{37665}).count() * dsec{0.0011232});
if (tp < sys_days(1964_y/April/1))
return duration_cast<Duration>(
dsec{3.240130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1964_y/September/1))
return duration_cast<Duration>(
dsec{3.340130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1965_y/January/1))
return duration_cast<Duration>(
dsec{3.440130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1965_y/March/1))
return duration_cast<Duration>(
dsec{3.540130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1965_y/July/1))
return duration_cast<Duration>(
dsec{3.640130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1965_y/September/1))
return duration_cast<Duration>(
dsec{3.740130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1966_y/January/1))
return duration_cast<Duration>(
dsec{3.840130} + (mjd(tp) - days{38761}).count() * dsec{0.001296});
if (tp < sys_days(1968_y/February/1))
return duration_cast<Duration>(
dsec{4.313170} + (mjd(tp) - days{39126}).count() * dsec{0.002592});
return duration_cast<Duration>(
dsec{4.213170} + (mjd(tp) - days{39126}).count() * dsec{0.002592});
}
} // namespace detail
template <class Duration>
inline
utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
@ -2065,7 +2132,8 @@ tai_clock::to_utc(const tai_time<Duration>& t) NOEXCEPT
using namespace std::chrono;
using CD = typename std::common_type<Duration, seconds>::type;
return utc_time<CD>{t.time_since_epoch()} -
(sys_days(year{1970}/January/1) - sys_days(year{1958}/January/1) + seconds{10});
(sys_days(year{1970}/January/1) - sys_days(year{1958}/January/1) +
detail::pre_leap<CD>(sys_time<CD>(to_local(t).time_since_epoch())));
}
template <class Duration>
@ -2076,7 +2144,8 @@ tai_clock::from_utc(const utc_time<Duration>& t) NOEXCEPT
using namespace std::chrono;
using CD = typename std::common_type<Duration, seconds>::type;
return tai_time<CD>{t.time_since_epoch()} +
(sys_days(year{1970}/January/1) - sys_days(year{1958}/January/1) + seconds{10});
(sys_days(year{1970}/January/1) - sys_days(year{1958}/January/1) +
detail::pre_leap<CD>(sys_time<CD>(t.time_since_epoch())));
}
inline
@ -2178,6 +2247,34 @@ template <class Duration>
using gps_seconds = gps_time<std::chrono::seconds>;
#if 1
template <class Duration>
inline
utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
gps_clock::to_utc(const gps_time<Duration>& t) NOEXCEPT
{
using namespace std::chrono;
using CD = typename std::common_type<Duration, seconds>::type;
return tai_clock::to_utc(tai_time<CD>{t.time_since_epoch()} +
(sys_days(year{1980}/January/Sunday[1]) - sys_days(year{1958}/January/1) +
seconds{19}));
}
template <class Duration>
inline
gps_time<typename std::common_type<Duration, std::chrono::seconds>::type>
gps_clock::from_utc(const utc_time<Duration>& t) NOEXCEPT
{
using namespace std::chrono;
using CD = typename std::common_type<Duration, seconds>::type;
return gps_time<CD>{tai_clock::from_utc(t).time_since_epoch()} -
(sys_days(year{1980}/January/Sunday[1]) - sys_days(year{1958}/January/1) +
seconds{19});
}
#else
template <class Duration>
inline
utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
@ -2202,6 +2299,8 @@ gps_clock::from_utc(const utc_time<Duration>& t) NOEXCEPT
seconds{9});
}
#endif
inline
gps_clock::time_point
gps_clock::now()

2
test/clock_cast_test/local_t.pass.cpp
View File

@ -82,7 +82,7 @@ main()
assert(clock_cast<local_t>(tt) == lt);
assert(tt.time_since_epoch() == seconds(0));
auto lu = local_days{1958_y/January/1_d} - seconds(10);
auto lu = local_days{1958_y/January/1_d};
auto ut = clock_cast<utc_clock>(lu);
assert(clock_cast<tai_clock>(ut) == tt);
}