How to convert epoch time ( seconds since 01/01/1970 00:00:00) to time_point

In some place I already get the epoch time value like this:

int64_t timeSeconds = std::chrono::duration_cast<std::chrono::seconds>(m_startTime.time_since_epoch()).count()

But how to convert this back to "std::chrono::system_clock::time_point"