Prefer `{Date,Time}.current` over `.today`/`.now`

`Date.current` and `Time.current` take `Time.zone` and
`config.time_zone` into account, falling back to `Date.today` and
`Time.now` respectively if a zone isn't set.
@pbrisbin I use Caleb's `vim-whitewash` to remove trailing whitespace on buffer writes. I guess it does it no matter the language. If needed, I could revert the whitespace back into place.