from_time_t(t1 + t2) gains incorrect and different results on Windows and Linux

OS: `Windows 7 x64 `
Compilers: `MSVC 2017 15.9.19`, `GCC 4.9.3`
boost: `1.72.0`

#include

namespace boost_ptime = boost::posix_time;

std::istringstream iss1{ "%H:%M:%S" };
iss1.imbue(std::locale(std::locale::classic(), new boost_ptime::time_input_facet("07:00:00")));
boost_ptime::ptime time_value1;
iss1 >> time_value1;

std::time_t t1 = 0;
if (!time_value1.is_not_a_date_time()) {
t1 = boost_ptime::to_time_t(time_value1);
}

std::istringstream iss2{ "%Y-%m-%d" };
iss2.imbue(std::locale(std::locale::classic(), new boost_ptime::time_input_facet("2019-06-17")));
boost_ptime::ptime time_value2;
iss2 >> time_value2;

std::time_t t2 = 0;
if (!time_value2.is_not_a_date_time()) {
t2 = boost_ptime::to_time_t(time_value2);
}

std::ostringstream oss;
oss.imbue(std::locale(std::locale::classic(), new boost_ptime::time_facet("%d.%m.%y %H:%M:%S")));
boost_ptime::ptime time_value3 = boost_ptime::from_time_t(t1 + t2);
oss << time_value3;

if (!oss.fail()) {
printf("%s\n", oss.str().c_str());
}

On Windows it prints:

```
27.10.18 03:46:08
```

On Linux it crashes (sometimes not, but gains a different result):

```
terminate called after throwing an instance of 'boost::wrapexcept'
what(): Year is out of valid range: 1400..9999
```

The same code over a standard library (`std::get_time`, `std::put_time`) works as expected.