diff --git a/Cargo.toml b/Cargo.toml
index 9b4db35a60..a25d939fcb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,12 +1,13 @@
 [package]
 name = "chrono"
-version = "0.1.4"
+version = "0.1.5"
 authors = ["Kang Seonghoon <public+rust@mearie.org>"]
 
 description = "Date and time library for Rust"
 homepage = "https://github.com/lifthrasiir/rust-chrono"
 documentation = "https://lifthrasiir.github.io/rust-chrono/chrono/"
 repository = "https://github.com/lifthrasiir/rust-chrono"
+keywords = ["date", "time", "calendar"]
 readme = "README.md"
 license = "MIT/Apache-2.0"
 
diff --git a/src/date.rs b/src/date.rs
index e75cdcd6ad..eb4bcf1f0e 100644
--- a/src/date.rs
+++ b/src/date.rs
@@ -262,25 +262,23 @@ impl<Off:Offset> hash::Hash for Date<Off> {
 }
 
 impl<Off:Offset> Add<Duration,Date<Off>> for Date<Off> {
-    fn add(&self, rhs: &Duration) -> Date<Off> {
-        Date { date: self.date + *rhs, offset: self.offset.clone() }
+    fn add(self, rhs: Duration) -> Date<Off> {
+        Date { date: self.date + rhs, offset: self.offset }
     }
 }
 
 impl<Off:Offset> Add<Date<Off>,Date<Off>> for Duration {
     #[inline]
-    fn add(&self, rhs: &Date<Off>) -> Date<Off> { rhs.add(self) }
+    fn add(self, rhs: Date<Off>) -> Date<Off> { rhs.add(self) }
 }
 
 impl<Off:Offset, Off2:Offset> Sub<Date<Off2>,Duration> for Date<Off> {
-    fn sub(&self, rhs: &Date<Off2>) -> Duration {
-        self.date - rhs.date
-    }
+    fn sub(self, rhs: Date<Off2>) -> Duration { self.date - rhs.date }
 }
 
 impl<Off:Offset> Sub<Duration,Date<Off>> for Date<Off> {
     #[inline]
-    fn sub(&self, rhs: &Duration) -> Date<Off> { self.add(&-*rhs) }
+    fn sub(self, rhs: Duration) -> Date<Off> { self.add(-rhs) }
 }
 
 impl<Off:Offset> fmt::Show for Date<Off> {
diff --git a/src/datetime.rs b/src/datetime.rs
index 24e9b7bdcb..b86e0d1180 100644
--- a/src/datetime.rs
+++ b/src/datetime.rs
@@ -183,25 +183,23 @@ impl<Off:Offset> hash::Hash for DateTime<Off> {
 }
 
 impl<Off:Offset> Add<Duration,DateTime<Off>> for DateTime<Off> {
-    fn add(&self, rhs: &Duration) -> DateTime<Off> {
-        DateTime { datetime: self.datetime + *rhs, offset: self.offset.clone() }
+    fn add(self, rhs: Duration) -> DateTime<Off> {
+        DateTime { datetime: self.datetime + rhs, offset: self.offset }
     }
 }
 
 impl<Off:Offset> Add<DateTime<Off>,DateTime<Off>> for Duration {
     #[inline]
-    fn add(&self, rhs: &DateTime<Off>) -> DateTime<Off> { rhs.add(self) }
+    fn add(self, rhs: DateTime<Off>) -> DateTime<Off> { rhs.add(self) }
 }
 
 impl<Off:Offset, Off2:Offset> Sub<DateTime<Off2>,Duration> for DateTime<Off> {
-    fn sub(&self, rhs: &DateTime<Off2>) -> Duration {
-        self.datetime - rhs.datetime
-    }
+    fn sub(self, rhs: DateTime<Off2>) -> Duration { self.datetime - rhs.datetime }
 }
 
 impl<Off:Offset> Sub<Duration,DateTime<Off>> for DateTime<Off> {
     #[inline]
-    fn sub(&self, rhs: &Duration) -> DateTime<Off> { self.add(&-*rhs) }
+    fn sub(self, rhs: Duration) -> DateTime<Off> { self.add(-rhs) }
 }
 
 impl<Off:Offset> fmt::Show for DateTime<Off> {
diff --git a/src/format.rs b/src/format.rs
index 30aea655f5..a3f6a09cc4 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -52,8 +52,8 @@ fn format(w: &mut Writer, date: Option<&NaiveDate>, time: Option<&NaiveTime>,
             (Some('Y'), Some(d), _, _) => try!(write!(w, "{}", d.year())),
             (Some('C'), Some(d), _, _) => try!(write!(w, "{:02}", d.year() / 100)),
             (Some('y'), Some(d), _, _) => try!(write!(w, "{:02}", d.year() % 100)),
-            (Some('G'), Some(d), _, _) => try!(write!(w, "{:04}", d.isoweekdate().val0())),
-            (Some('g'), Some(d), _, _) => try!(write!(w, "{:02}", d.isoweekdate().val0() % 100)),
+            (Some('G'), Some(d), _, _) => try!(write!(w, "{:04}", d.isoweekdate().0)),
+            (Some('g'), Some(d), _, _) => try!(write!(w, "{:02}", d.isoweekdate().0 % 100)),
 
             // month
             (Some('m'), Some(d), _, _) => try!(write!(w, "{:02}", d.month())),
@@ -73,7 +73,7 @@ fn format(w: &mut Writer, date: Option<&NaiveDate>, time: Option<&NaiveTime>,
             (Some('W'), Some(d), _, _) =>
                 try!(write!(w, "{:02}", (d.ordinal() - d.weekday().num_days_from_monday()
                                                      + 7) / 7)),
-            (Some('V'), Some(d), _, _) => try!(write!(w, "{:02}", d.isoweekdate().val1())),
+            (Some('V'), Some(d), _, _) => try!(write!(w, "{:02}", d.isoweekdate().1)),
 
             // day of week
             (Some('a'), Some(d), _, _) =>
@@ -98,12 +98,12 @@ fn format(w: &mut Writer, date: Option<&NaiveDate>, time: Option<&NaiveTime>,
             // hour
             (Some('H'), _, Some(t), _) => try!(write!(w, "{:02}", t.hour())),
             (Some('k'), _, Some(t), _) => try!(write!(w, "{:2}", t.hour())),
-            (Some('I'), _, Some(t), _) => try!(write!(w, "{:02}", t.hour12().val1())),
-            (Some('l'), _, Some(t), _) => try!(write!(w, "{:2}", t.hour12().val1())),
+            (Some('I'), _, Some(t), _) => try!(write!(w, "{:02}", t.hour12().1)),
+            (Some('l'), _, Some(t), _) => try!(write!(w, "{:2}", t.hour12().1)),
             (Some('P'), _, Some(t), _) =>
-                try!(write!(w, "{}", if t.hour12().val0() {"pm"} else {"am"})),
+                try!(write!(w, "{}", if t.hour12().0 {"pm"} else {"am"})),
             (Some('p'), _, Some(t), _) =>
-                try!(write!(w, "{}", if t.hour12().val0() {"PM"} else {"AM"})),
+                try!(write!(w, "{}", if t.hour12().0 {"PM"} else {"AM"})),
 
             // minute
             (Some('M'), _, Some(t), _) => try!(write!(w, "{:02}", t.minute())),
diff --git a/src/naive/date.rs b/src/naive/date.rs
index 7482a4a90d..8cb5f74054 100644
--- a/src/naive/date.rs
+++ b/src/naive/date.rs
@@ -378,7 +378,7 @@ impl Datelike for NaiveDate {
 }
 
 impl Add<Duration,NaiveDate> for NaiveDate {
-    fn add(&self, rhs: &Duration) -> NaiveDate {
+    fn add(self, rhs: Duration) -> NaiveDate {
         // TODO overflow currently fails
 
         let year = self.year();
@@ -397,11 +397,11 @@ impl Add<Duration,NaiveDate> for NaiveDate {
 
 impl Add<NaiveDate,NaiveDate> for Duration {
     #[inline]
-    fn add(&self, rhs: &NaiveDate) -> NaiveDate { rhs.add(self) }
+    fn add(self, rhs: NaiveDate) -> NaiveDate { rhs.add(self) }
 }
 
 impl Sub<NaiveDate,Duration> for NaiveDate {
-    fn sub(&self, rhs: &NaiveDate) -> Duration {
+    fn sub(self, rhs: NaiveDate) -> Duration {
         let year1 = self.year();
         let year2 = rhs.year();
         let (year1_div_400, year1_mod_400) = div_mod_floor(year1, 400);
@@ -414,7 +414,7 @@ impl Sub<NaiveDate,Duration> for NaiveDate {
 
 impl Sub<Duration,NaiveDate> for NaiveDate {
     #[inline]
-    fn sub(&self, rhs: &Duration) -> NaiveDate { self.add(&-*rhs) }
+    fn sub(self, rhs: Duration) -> NaiveDate { self.add(-rhs) }
 }
 
 impl fmt::Show for NaiveDate {
diff --git a/src/naive/datetime.rs b/src/naive/datetime.rs
index 1e22543546..e6e9c633be 100644
--- a/src/naive/datetime.rs
+++ b/src/naive/datetime.rs
@@ -163,11 +163,11 @@ impl Timelike for NaiveDateTime {
 }
 
 impl Add<Duration,NaiveDateTime> for NaiveDateTime {
-    fn add(&self, rhs: &Duration) -> NaiveDateTime {
+    fn add(self, rhs: Duration) -> NaiveDateTime {
         // Duration does not directly give its parts, so we need some additional calculations.
         let days = rhs.num_days();
-        let nanos = (*rhs - Duration::days(days)).num_nanoseconds().unwrap();
-        debug_assert!(Duration::days(days) + Duration::nanoseconds(nanos) == *rhs);
+        let nanos = (rhs - Duration::days(days)).num_nanoseconds().unwrap();
+        debug_assert!(Duration::days(days) + Duration::nanoseconds(nanos) == rhs);
         debug_assert!(-86400_000_000_000 < nanos && nanos < 86400_000_000_000);
 
         let mut date = self.date + Duration::days(days);
@@ -185,18 +185,18 @@ impl Add<Duration,NaiveDateTime> for NaiveDateTime {
 
 impl Add<NaiveDateTime,NaiveDateTime> for Duration {
     #[inline]
-    fn add(&self, rhs: &NaiveDateTime) -> NaiveDateTime { rhs.add(self) }
+    fn add(self, rhs: NaiveDateTime) -> NaiveDateTime { rhs.add(self) }
 }
 
 impl Sub<NaiveDateTime,Duration> for NaiveDateTime {
-    fn sub(&self, rhs: &NaiveDateTime) -> Duration {
+    fn sub(self, rhs: NaiveDateTime) -> Duration {
         (self.date - rhs.date) + (self.time - rhs.time)
     }
 }
 
 impl Sub<Duration,NaiveDateTime> for NaiveDateTime {
     #[inline]
-    fn sub(&self, rhs: &Duration) -> NaiveDateTime { self.add(&-*rhs) }
+    fn sub(self, rhs: Duration) -> NaiveDateTime { self.add(-rhs) }
 }
 
 impl fmt::Show for NaiveDateTime {
diff --git a/src/naive/time.rs b/src/naive/time.rs
index c9f64cd39e..a1f8ff8364 100644
--- a/src/naive/time.rs
+++ b/src/naive/time.rs
@@ -133,9 +133,9 @@ impl NaiveTime {
 }
 
 impl Timelike for NaiveTime {
-    #[inline] fn hour(&self) -> u32 { self.hms().val0() }
-    #[inline] fn minute(&self) -> u32 { self.hms().val1() }
-    #[inline] fn second(&self) -> u32 { self.hms().val2() }
+    #[inline] fn hour(&self) -> u32 { self.hms().0 }
+    #[inline] fn minute(&self) -> u32 { self.hms().1 }
+    #[inline] fn second(&self) -> u32 { self.hms().2 }
     #[inline] fn nanosecond(&self) -> u32 { self.frac }
 
     #[inline]
@@ -172,10 +172,10 @@ impl Timelike for NaiveTime {
 }
 
 impl Add<Duration,NaiveTime> for NaiveTime {
-    fn add(&self, rhs: &Duration) -> NaiveTime {
+    fn add(self, rhs: Duration) -> NaiveTime {
         // there is no direct interface in `Duration` to get only the nanosecond part,
         // so we need to do the additional calculation here.
-        let rhs2 = *rhs - Duration::seconds(rhs.num_seconds());
+        let rhs2 = rhs - Duration::seconds(rhs.num_seconds());
         let mut secs = self.secs + (rhs.num_seconds() % 86400 + 86400) as u32;
         let mut nanos = self.frac + rhs2.num_nanoseconds().unwrap() as u32;
 
@@ -192,11 +192,11 @@ impl Add<Duration,NaiveTime> for NaiveTime {
 
 impl Add<NaiveTime,NaiveTime> for Duration {
     #[inline]
-    fn add(&self, rhs: &NaiveTime) -> NaiveTime { rhs.add(self) }
+    fn add(self, rhs: NaiveTime) -> NaiveTime { rhs.add(self) }
 }
 
 impl Sub<NaiveTime,Duration> for NaiveTime {
-    fn sub(&self, rhs: &NaiveTime) -> Duration {
+    fn sub(self, rhs: NaiveTime) -> Duration {
         // the number of whole non-leap seconds
         let secs = self.secs as i64 - rhs.secs as i64 - 1;
 
@@ -214,7 +214,7 @@ impl Sub<NaiveTime,Duration> for NaiveTime {
 
 impl Sub<Duration,NaiveTime> for NaiveTime {
     #[inline]
-    fn sub(&self, rhs: &Duration) -> NaiveTime { self.add(&-*rhs) }
+    fn sub(self, rhs: Duration) -> NaiveTime { self.add(-rhs) }
 }
 
 impl fmt::Show for NaiveTime {
diff --git a/src/time.rs b/src/time.rs
index 79103875f7..74c91d683b 100644
--- a/src/time.rs
+++ b/src/time.rs
@@ -111,25 +111,23 @@ impl<Off:Offset> hash::Hash for Time<Off> {
 }
 
 impl<Off:Offset> Add<Duration,Time<Off>> for Time<Off> {
-    fn add(&self, rhs: &Duration) -> Time<Off> {
-        Time { time: self.time + *rhs, offset: self.offset.clone() }
+    fn add(self, rhs: Duration) -> Time<Off> {
+        Time { time: self.time + rhs, offset: self.offset }
     }
 }
 
 impl<Off:Offset> Add<Time<Off>,Time<Off>> for Duration {
     #[inline]
-    fn add(&self, rhs: &Time<Off>) -> Time<Off> { rhs.add(self) }
+    fn add(self, rhs: Time<Off>) -> Time<Off> { rhs.add(self) }
 }
 
 impl<Off:Offset, Off2:Offset> Sub<Time<Off2>,Duration> for Time<Off> {
-    fn sub(&self, rhs: &Time<Off2>) -> Duration {
-        self.time - rhs.time
-    }
+    fn sub(self, rhs: Time<Off2>) -> Duration { self.time - rhs.time }
 }
 
 impl<Off:Offset> Sub<Duration,Time<Off>> for Time<Off> {
     #[inline]
-    fn sub(&self, rhs: &Duration) -> Time<Off> { self.add(&-*rhs) }
+    fn sub(self, rhs: Duration) -> Time<Off> { self.add(-rhs) }
 }
 
 impl<Off:Offset> fmt::Show for Time<Off> {