The Unix timestamp will begin with 16 this Sunday
It is going to be at 2020-09-13 12:26:40 UTC.Python:  $ python3 -q
  >>> from datetime import datetime
  >>> datetime.utcfromtimestamp(1_600_000_000)
  datetime.datetime(2020, 9, 13, 12, 26, 40)

GNU date (Linux):  $ date -ud @1600000000
  Sun Sep 13 12:26:40 UTC 2020

BSD date (macOS, FreeBSD, OpenBSD, etc.):  $ date -ur 1600000000
  Sun Sep 13 12:26:40 UTC 2020

All such dates (in UTC) until the end of the current century:  $ python3 -q
  >>> from datetime import datetime
  >>> for t in range(0, 4_200_000_000, 100_000_000): print(f'{t:13_d} - {datetime.utcfromtimestamp(t).strftime("%Y-%m-%d %H:%M:%S")}')
  ...
              0 - 1970-01-01 00:00:00
    100_000_000 - 1973-03-03 09:46:40
    200_000_000 - 1976-05-03 19:33:20
    300_000_000 - 1979-07-05 05:20:00
    400_000_000 - 1982-09-04 15:06:40
    500_000_000 - 1985-11-05 00:53:20
    600_000_000 - 1989-01-05 10:40:00
    700_000_000 - 1992-03-07 20:26:40
    800_000_000 - 1995-05-09 06:13:20
    900_000_000 - 1998-07-09 16:00:00
  1_000_000_000 - 2001-09-09 01:46:40
  1_100_000_000 - 2004-11-09 11:33:20
  1_200_000_000 - 2008-01-10 21:20:00
  1_300_000_000 - 2011-03-13 07:06:40
  1_400_000_000 - 2014-05-13 16:53:20
  1_500_000_000 - 2017-07-14 02:40:00
  1_600_000_000 - 2020-09-13 12:26:40
  1_700_000_000 - 2023-11-14 22:13:20
  1_800_000_000 - 2027-01-15 08:00:00
  1_900_000_000 - 2030-03-17 17:46:40
  2_000_000_000 - 2033-05-18 03:33:20
  2_100_000_000 - 2036-07-18 13:20:00
  2_200_000_000 - 2039-09-18 23:06:40
  2_300_000_000 - 2042-11-19 08:53:20
  2_400_000_000 - 2046-01-19 18:40:00
  2_500_000_000 - 2049-03-22 04:26:40
  2_600_000_000 - 2052-05-22 14:13:20
  2_700_000_000 - 2055-07-24 00:00:00
  2_800_000_000 - 2058-09-23 09:46:40
  2_900_000_000 - 2061-11-23 19:33:20
  3_000_000_000 - 2065-01-24 05:20:00
  3_100_000_000 - 2068-03-26 15:06:40
  3_200_000_000 - 2071-05-28 00:53:20
  3_300_000_000 - 2074-07-28 10:40:00
  3_400_000_000 - 2077-09-27 20:26:40
  3_500_000_000 - 2080-11-28 06:13:20
  3_600_000_000 - 2084-01-29 16:00:00
  3_700_000_000 - 2087-04-01 01:46:40
  3_800_000_000 - 2090-06-01 11:33:20
  3_900_000_000 - 2093-08-01 21:20:00
  4_000_000_000 - 2096-10-02 07:06:40
  4_100_000_000 - 2099-12-03 16:53:20