The BIH scale, A.1, and NBS-A were defined by an epoch at the beginning of 1958 The procedures used by the BIH evolved, and the name for the time scale changed: A3 in 1964 and TA(BIH) in 1969.
ðə bˌiːˌaɪˈeɪtʃ skˈeɪl, ˈeɪ.wˈʌn, ænd ˌɛnbˌiːˈɛsɐ wɜː dᵻfˈaɪnd baɪ ɐn ˈɛpɑːk æt ðə bɪɡˈɪnɪŋ ʌv nˈaɪntiːnhˈʌndɹɪd fˈɪfti ˈeɪt ðə pɹəsˈiːdʒɚz jˈuːzd baɪ ðə bˌiːˌaɪˈeɪtʃ ɪvˈɑːlvd, ænd ðə nˈeɪm fɚðə tˈaɪm skˈeɪl tʃˈeɪndʒd: ˌeɪ θɹˈiː ɪn nˈaɪntiːnhˈʌndɹɪd sˈɪksti fˈoːɹ ænd tˌiːˈeɪ bˌiːˌaɪˈeɪtʃ ɪn nˈaɪntiːnhˈʌndɹɪd sˈɪksti nˈaɪn.