diff --git a/src/lib.rs b/src/lib.rs
index e85f222..f24109a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,9 @@
 #[macro_use] extern crate quick_error;
 use chrono::{ Local,prelude::*, };
 
+use std::str::Chars;
+use std::iter::Peekable;
+
 quick_error! {
     #[derive(Debug)]
     pub enum ParseError {
@@ -10,42 +13,108 @@ quick_error! {
     }
 }
 
+#[derive(Debug)]
 enum SimpleDateFormatPart {
-    Year,
-    Month,
+    YearLower(usize),
+    YearUpper(usize),
+    MonthLower(usize),
+    MonthUpper(usize),
     Day,
     Hour,
     Minute,
     Second,
+    LiteralChar(char),
     Literal(String),
 }
 
+#[derive(Debug)]
 pub struct SimpleDateFormat {
     parts: Vec<SimpleDateFormatPart>,
 }
 
 impl SimpleDateFormat {
 
-    fn format_local(&self, date_time: &DateTime<Local>) -> String {
+    pub fn format_local(&self, date_time: &DateTime<Local>) -> String {
         let mut ret = String::with_capacity(512);
-        ret.push_str(&format!("{}", date_time.year()));
-        ret.push('-');
-        ret.push_str(&format!("{}", date_time.month()));
-        ret.push('-');
-        ret.push_str(&format!("{}", date_time.day()));
+
+        for part in &self.parts {
+            match part {
+                SimpleDateFormatPart::LiteralChar(c) => ret.push(*c),
+                SimpleDateFormatPart::Literal(s) => ret.push_str(s),
+                SimpleDateFormatPart::YearLower(cnt) => ret.push_str(&format_str(date_time.year(), *cnt)),
+                SimpleDateFormatPart::MonthLower(cnt) => ret.push_str(&format_str(date_time.month() as i32, *cnt)),
+                _ => (),
+            }
+        }
         ret
     }
 }
 
 pub fn fmt(f: &str) -> Result<SimpleDateFormat, ParseError> {
-    Ok(SimpleDateFormat{ parts: vec![] })
+    let mut parts = vec![];
+
+    let mut is_in_quotation_mark = false;
+    let mut literal = String::new();
+    let mut chars = f.chars().peekable();
+    while let Some(c) = chars.next() {
+        if is_in_quotation_mark && c != '\'' {
+            literal.push(c);
+            continue;
+        }
+        match c {
+            '\'' => if is_in_quotation_mark {
+                if let Some('\'') = chars.peek() {
+                    literal.push(c);
+                    chars.next(); // eat '\''
+                } else {
+                    is_in_quotation_mark = false;
+                    parts.push(SimpleDateFormatPart::Literal(literal));
+                    literal = String::new();
+                }
+            } else {
+                is_in_quotation_mark = true;
+            },
+            ',' | '.' | ':' | '-' | ' ' => parts.push(SimpleDateFormatPart::LiteralChar(c)),
+            'y' => parts.push(SimpleDateFormatPart::YearLower(get_all_chars(c, &mut chars))),
+            'Y' => parts.push(SimpleDateFormatPart::YearUpper(get_all_chars(c, &mut chars))),
+            'm' => parts.push(SimpleDateFormatPart::MonthLower(get_all_chars(c, &mut chars))),
+            'M' => parts.push(SimpleDateFormatPart::MonthUpper(get_all_chars(c, &mut chars))),
+            _ => (),
+        }
+    }
+
+    Ok(SimpleDateFormat{ parts })
     // Err(ParseError::Format(f.into()))
 }
 
+fn format_str(n: i32, cnt: usize) -> String {
+    let ret = format!("{}", n);
+    if cnt > ret.len() {
+        "0".repeat(cnt - ret.len()) + &ret
+    } else {
+        ret
+    }
+}
+
+fn get_all_chars(c: char, chars: &mut Peekable<Chars>) -> usize {
+    let mut cnt = 1_usize;
+    while let Some(next_char) = chars.peek() {
+        if *next_char == c {
+            cnt += 1;
+            chars.next();
+        } else {
+            break;
+        }
+    }
+    cnt
+}
 
 #[test]
 fn it_works() {
-    println!("test output: {}", fmt("").unwrap().format_local(&Local::now()));
+    // println!("test output: {}", fmt("").unwrap().format_local(&Local::now()));
+
+    println!("{:?}", fmt("y yy-mm 'mm '''"));
+    println!("{:?}", fmt("y yy-mm'(-'m')' '[mm]'").unwrap().format_local(&Local::now()));
 
     assert_eq!(2 + 2, 4);
 }