Date subcommands (#2383)

* refactored date command

* format files

crates/nu-cli/src/commands.rs

@@ -147,7 +147,7 @@ pub(crate) use config::{
 };
 pub(crate) use count::Count;
 pub(crate) use cp::Cpy;
-pub(crate) use date::Date;
+pub(crate) use date::{DateFormat, DateNow, DateUTC};
 pub(crate) use debug::Debug;
 pub(crate) use default::Default;
 pub(crate) use do_::Do;