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.