The instant that the gravitational correction started to be applied serves as the epoch for Barycentric Coordinate Time (TCB), Geocentric Coordinate Time (TCG), and Terrestrial Time (TT), which represent three fundamental time scales in the solar system.
ðɪ ˈɪnstənt ðætðə ɡɹˌævɪtˈeɪʃənəl kɚɹˈɛkʃən stˈɑːɹɾᵻd təbi ɐplˈaɪd sˈɜːvz æz ðɪ ˈɛpɑːk fɔːɹ bɑːɹɹˈaɪsəntɹˌɪk koʊˈɔːɹdᵻnət tˈaɪm tˌiːsˌiːbˈiː, dʒˌiːoʊsˈɛntɹɪk koʊˈɔːɹdᵻnət tˈaɪm tˌiːsˌiːdʒˈiː, ænd tɚɹˈɛstɹɪəl tˈaɪm tˌiːtˈiː, wˌɪtʃ ɹˌɛpɹᵻzˈɛnt θɹˈiː fˌʌndəmˈɛntəl tˈaɪm skˈeɪlz ɪnðə sˈoʊlɚ sˈɪstəm.