1 Kalpa (4.3 Billion Years)of Brahma matches the age of earth approx. which is 4.54 Billion Years. But in the 2nd Kalpa or the night of Brahma (after 4.3 Billion Years), Brahma sleeps and there is total annihilation. So in that case, after this age of earth, the earth should be totally destroyed again? But we are all still alive? Why so?
Because Time is cyclic in nature as per Hinduism. Creation, preservation and destruction is happenning since eternity.
चतुर्-युग-सहस्रं तु ब्रह्मणो दिनम् उच्यते स कल्पो यत्र मनवश्च तुर्दश विशाम्-पते||
One thousand cycles of four ages constitute a single day of Brahmā, known as a kalpa. In that period, O King, fourteen Manus come and go.
So, 1 kalpa is 1000* 12,000* 360 = 4.32 billion years as said by you. After pralaya, Three worlds (Swarga, Earth and Patala) are again created by Brahma (which is next day for Lord Brahma).
निशावसान आरब्धो लोक-कल्पो ’नुवर्तते यावद् दिनं भगवतो मनून् भुञ्जंश् चतुर्-दश||
After the end of Brahmā’s night, the creation of the three worlds begins again in the daytime of Brahmā, and they continue to exist through the life durations of fourteen consecutive Manus, or fathers of mankind.
Same is the case with Mahapralaya. So, time is cyclic in nature with no beginning.