its manual testing but it is working

src/main.rs

@@ -2,7 +2,7 @@ use serde::{Serialize, Deserialize};
 use std::io::{Read, Write};
 use std::fs::File;
 use std::time::{SystemTime, UNIX_EPOCH, Duration};
-use std::ops::Add;
+use std::ops::{Add, Sub};
 use clap::Parser;
 
 #[derive(Debug, Parser)]
@@ -13,6 +13,9 @@ struct Flags {
    #[arg(short = 'l', long = "log")]
    log: bool,
 
+   #[arg(short = 's', long = "since")]
+   since: Option<String>,
+
    #[arg(short = 'a', long = "add")]
    add: Option<String>,
 
@@ -23,18 +26,42 @@ struct Flags {
 fn main() {
    let flags = Flags::parse();
 
-   match flags.add.clone() {
+   add(&flags.f, &flags.add, &flags.tag).unwrap();
-      Some(add) => {
+   log(&flags.f, &flags.since).unwrap();
-         let tag = flags.tag.clone().unwrap_or("".to_string());
 
-         let mut tsheet = load(flags.f.clone()).unwrap();
+   println!("{:?}", flags);
-         tsheet.add(add, tag);
+}
-         save(flags.f.clone(), tsheet).unwrap();
+
+fn add(f: &String, x: &Option<String>, tag: &Option<String>) -> Result<(), String> {
+   match x {
+      Some(x) => {
+         let mut tsheet = load(&f)?;
+         tsheet.add(
+            x.to_string(),
+            tag.clone().unwrap_or("".to_string()),
+         );
+         save(&f, tsheet)?;
       },
       None => {},
    };
+   Ok(())
+}
 
-   println!("{:?}", flags);
+fn log(f: &String, since: &Option<String>) -> Result<(), String> {
+   let since = parse_time(since)?;
+   let tsheet = load(&f)?;
+   let tsheet = tsheet.since(since);
+   println!("{:?}", tsheet);
+   Err("not impl".to_string())
+}
+
+fn parse_time(since: &Option<String>) -> Result<SystemTime, String> {
+   match since {
+      Some(since) => {
+         Err("not impl".to_string())
+      },
+      None => Ok(SystemTime::now().sub(Duration::from_secs(60*60*24*7))),
+   }
 }
 
 #[derive(Debug, PartialEq, Serialize, Deserialize)]
@@ -49,7 +76,7 @@ struct X {
    tag: String,
 }
 
-fn save(path: String, tsheet: TSheet) -> Result<(), String> {
+fn save(path: &String, tsheet: TSheet) -> Result<(), String> {
    match File::create(path.clone()) {
       Ok(mut writer) => _save(&mut writer, tsheet),
       Err(reason) => Err(format!("failed to open {} to save tsheet: {}", path, reason)),
@@ -64,7 +91,7 @@ fn _save(writer: &mut dyn Write, tsheet: TSheet) -> Result<(), String> {
    }
 }
 
-fn load(path: String) -> Result<TSheet, String> {
+fn load(path: &String) -> Result<TSheet, String> {
    match File::open(path.clone()) {
       Ok(mut reader) => _load(&mut reader),
       Err(reason) => Err(format!("failed to read tsheet {}: {}", path, reason)),