
  -spec erlang:system_time(Unit) -> integer() when Unit :: time_unit().

Since:
  OTP 18.0

  Returns current Erlang system time converted into the Unit
  passed as argument.

  Calling erlang:system_time(Unit) is equivalent to 
  erlang:convert_time_unit(erlang:system_time(), native, Unit).

  Note:
    This time is not a monotonically increasing time in the
    general case. For more information, see the documentation of 
    time warp modes in the User's Guide.
