std.datetime

[drug via Digitalmars-d-learn]

unittest
{
        import std.datetime : SysTime, UTC;

        {
                auto st = SysTime();
                st.timezone(UTC());

                long date  = 
st.fromISOExtString("2017-02-10T00:00:00Z").stdTime,
                        time_of_day = 
st.fromISOExtString("0000-01-01T23:59:50Z").stdTime,
                        timestamp   = 
st.fromISOExtString("0000-01-01T23:59:55Z").stdTime;

                import std.stdio;
                st.stdTime(date);
                writeln(st);
                st.stdTime(timestamp);
                writeln(st);
                st.stdTime(date+timestamp);
                writeln(st);
        }
}

prints
```
2017-Feb-10 00:00:00Z
0000-Jan-01 23:59:55Z
2016-Feb-10 23:59:55Z
```
I expect
```
2017-Feb-10 00:00:00Z
0000-Jan-01 23:59:55Z
2017-Feb-10 23:59:55Z
```

Why does it decrement years? What do I do wrong?