TDB（太陽系重心力学時）
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<timefyi-glossary slug="tdb"></timefyi-glossary>定義
惑星の暦表で使用される相対論的時刻尺度で、太陽系の重心で測定される。TDBは地球の太陽からの距離変化による相対論的効果を考慮し、TT（地球時）との差は2ミリ秒未満。