/**
* Converts this instance to the Coordinated Universal Time scale (UTC), or
* if a time zone was set then that timezone
*
* @return static
* @throws Exception Occurs if UTC cannot be computed
*/
public function toUTC()
{
if ($this->timescale == TimeScale::UTC()) {
// Remove the timezone and set to UTC
$offset = $this->timezone->offset($this->toJD());
$this->sub(Time::hours($offset));
$this->timezone = $this->timezone0 ? $this->timezone0 : TimeZone::UTC();
return $this;
}
// TAI -> UTC
if ($this->timescale == TimeScale::TAI()) {
$tai1 = $this->jd;
$tai2 = $this->dayFrac;
IAU::Taiutc($tai1, $tai2, $utc1, $utc2);
$this->jd = $utc1;
$this->dayFrac = $utc2;
$this->timescale = TimeScale::UTC();
return $this;
}
// TT -> UTC
if ($this->timescale == TimeScale::TT()) {
$tt1 = $this->jd;
$tt2 = $this->dayFrac;
IAU::Tttai($tt1, $tt2, $tai1, $tai2);
IAU::Taiutc($tai1, $tai2, $utc1, $utc2);
$this->jd = $utc1;
$this->dayFrac = $utc2;
$this->timescale = TimeScale::UTC();
return $this;
}
// UT1 -> UTC
if ($this->timescale == TimeScale::UT1()) {
$ut11 = $this->jd;
$ut12 = $this->dayFrac;
$dut1 = IERS::jd($ut11 + $ut12)->dut1();
IAU::Ut1utc($ut11, $ut12, $dut1, $utc1, $utc2);
$this->jd = $utc1;
$this->dayFrac = $utc2;
$this->timescale = TimeScale::UTC();
return $this;
}
// TDB -> UTC
if ($this->timescale == TimeScale::TDB()) {
$tt1 = $this->jd;
$tt2 = $this->dayFrac;
$ut = $this->dayFrac;
$dtr = IAU::Dtdb($tt1, $tt2, $ut, 0, 0, 0);
$tdb1 = $this->jd;
$tdb2 = $this->dayFrac;
IAU::Tdbtt($tdb1, $tdb2, $dtr, $tt1, $tt2);
IAU::Tttai($tt1, $tt2, $tai1, $tai2);
IAU::Taiutc($tai1, $tai2, $utc1, $utc2);
$this->jd = $utc1;
$this->dayFrac = $utc2;
$this->timescale = TimeScale::UTC();
return $this;
}
throw new Exception('Error converting to UTC');
}
