src/Marando/AstroDate/AstroDate.php
public function toTAI()
    {
        if ($this->timescale == TimeScale::TAI()) {
            return $this;
        }

        $this->toUTC();

        $utc1 = $this->jd;
        $utc2 = $this->dayFrac;
        IAU::Utctai($utc1, $utc2, $tai1, $tai2);

        $this->jd        = $tai1;
        $this->dayFrac   = $tai2;
        $this->timescale = TimeScale::TAI();

        return $this;
    }
public function toTAI()
    {
        if ($this->timescale == TimeScale::TAI()) {
            return $this;
        }

        $this->toUTC();

        $utc1 = $this->jd;
        $utc2 = $this->dayFrac;
        IAU::Utctai($utc1, $utc2, $tai1, $tai2);

        $this->jd        = $tai1;
        $this->dayFrac   = $tai2;
        $this->timescale = TimeScale::TAI();

        return $this;
    }
Converts this instance to International Atomic Time (TAI)

@return static