You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.rs
    path of file: ./repos/coreutils/date/src
    
    the code of the file until where you have to start completion: use std::{path::Path, str::FromStr};

use clap::ArgMatches;
use coreutils_core::time::{
    Date, Duration, OffsetDateTime as DateTime, PrimitiveDateTime, Time, UtcOffset,
};

mod cli;

const DEFAULT_FMT_OUT: &str = "%a %b %d %H:%M:%S %z %Y";
const RFC_2822_FMT: &str = "%a, %d %b %Y %T %z";

fn main() {
    let matches = cli::create_a
    
fn reference_datetime(input: &str, utc_off: UtcOffset) -> Result<DateTime, String> {
    // First try to parse as a number, if it fails, treat as a file
    match input.trim().parse::<i64>() {
        Ok(sec) => Ok(DateTime::from_unix_timestamp(sec).to_offset(utc_off)),
        Err(p_err) => match datetime_from_file(input, utc_off) {
            Ok(d) => Ok(d),
            Err(f_err) => Err(format!(
                "Invalid read input: Neither a file or seconds: {} AND {}",
                f_err, p_err
            )),
        },
    }
}