Negative fractional times round toward zero #116

Date conversion casts the time in seconds with (time_t)inSeconds, which truncates toward zero, so any negative time with milliseconds lands on the wrong second: Date.fromTime(-500) is 1970-01-01 00:00:00 UTC instead of 1969-12-31 23:59:59, and Date.fromTime(-1500).getUTCSeconds() is 59 instead of 58. It should floor.