using Dates

function partial_year(period::Type{<:Period}, float::AbstractFloat)
    _year, Δ = divrem(float, 1)
    year_start = DateTime(_year)
    year = period((year_start + Year(1)) - year_start)
    partial = period(floor(Dates.value(year) * Δ))
    year_start + partial
end
partial_year(float::AbstractFloat) = partial_year(Nanosecond, float)

julia> partial_year(2018.003828474404)
2018-01-02T09:32:14.768

julia> partial_year(Minute, 2018.003828474404)
2018-01-02T09:32:00