It was used as a basis for calibrating the quartz clocks at the Royal Greenwich Observatory and to establish a time scale, called Greenwich Atomic (GA).
ɪt wʌz jˈuːzd æz ɐ bˈeɪsɪs fɔːɹ kˈælɪbɹˌeɪɾɪŋ ðə kwˈɔːɹts klˈɑːks æt ðə ɹˈɔɪəl ɡɹˈɛnɪtʃ əbzˈɜːvətˌoːɹi ænd tʊ ɪstˈæblɪʃ ɐ tˈaɪm skˈeɪl, kˈɔːld ɡɹˈɛnɪtʃ ɐtˈɑːmɪk dʒˌiːˈeɪ.