diff --git a/src/main.rs b/src/main.rs
index 7ffee6d..e4265e1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,29 +5,21 @@ use std::{env, io};
 fn main() -> io::Result<()> {
     let args: Vec<String> = env::args().collect();
 
-    // TODO: change expected length to rfc3339
-    // if args.len() == 1 || args[1].len() != 8 as usize {
-    //     println!("usage: since hh:mm:ss");
-    //     std::process::abort();
-    // }
+    if args.len() == 1
+        || !(args[1].len() == 8 as usize
+            || args[1].len() == 19 as usize
+            || args[1].len() == 21 as usize)
+    {
+        println!("usage: since hh:mm:ss"); //8
+        println!("usage: since yyyy-mm-dd hh:mm:ss"); //19
+        println!("usage: since <RFC 3339 timestamp>"); //21
+        std::process::abort();
+    }
 
     let buffer = &args[1];
 
-    //println!("{buffer}");
-
     let tz = *Local::now().offset();
 
-    // println!(
-    //     "{}",
-    //     NaiveDateTime::new(
-    //         Local::now().date_naive(),
-    //         NaiveTime::parse_from_str("12:00:00", "%H:%M:%S").unwrap()
-    //     )
-    //     .and_local_timezone(tz)
-    //     .single()
-    //     .unwrap()
-    // );
-
     let timestamp: DateTime<Local>;
     if let Some(t) = buffer.parse::<DateTime<Local>>().ok() {
         timestamp = t;
@@ -44,12 +36,8 @@ fn main() -> io::Result<()> {
         std::process::abort();
     }
 
-    // NOTE: is local appropriate here?
     let now = Local::now();
 
-    // println!("{}", timestamp.to_rfc3339());
-    // println!("{}", now.to_rfc3339());
-
     let delta = DateTime::signed_duration_since(now, timestamp);
 
     let days = ((delta.num_seconds() / 60) / 60) / 24;