fix(user/bkdatev):Pass date arguments to get_tz_offset()

- Note: If arguments to `bkdatev` are not passed to the `date` call in
  the `get_tz_offset()` function, the time zone offset displayed will be
  that of the user's current time, not the historical time they might
  specify via an option like `--date="1941-12-07T07:48-10:30"`; in this
  particular example, the reported time for Hawaii would be
  `1941-12-07T07:48-10` if the command were run in the year 2023 when
  Hawaii's time zone offset is `UTC-10` instead of `UT/GMT-10:30` as it
  was in the year 1941.