* Modified documentation examples

* Fixed typo in NaiveTime docs for Default

src/naive/date.rs

@@ -1714,16 +1714,16 @@ impl str::FromStr for NaiveDate {
     }
 }
 
-/// The default for a NaiveDate is 1st of January 1970.
+/// The default value for a NaiveDate is 1st of January 1970.
 ///
 /// # Example
 ///
-/// ~~~~
+/// ```rust
 /// use chrono::NaiveDate;
 ///
 /// let default_date = NaiveDate::default();
 /// assert_eq!(default_date, NaiveDate::from_ymd(1970, 1, 1));
-/// ~~~~
+/// ```
 impl Default for NaiveDate {
     fn default() -> Self {
         NaiveDate::from_ymd(1970, 1, 1)

src/naive/datetime.rs

@@ -1511,17 +1511,17 @@ impl str::FromStr for NaiveDateTime {
     }
 }
 
-/// The default for a NaiveDateTime is one with epoch 0
-/// that is 1st of January 1970 at 00:00:00.
+/// The default value for a NaiveDateTime is one with epoch 0
+/// that is, 1st of January 1970 at 00:00:00.
 ///
 /// # Example
 ///
-/// ~~~~
+/// ```rust
 /// use chrono::NaiveDateTime;
 ///
 /// let default_date = NaiveDateTime::default();
 /// assert_eq!(default_date, NaiveDateTime::from_timestamp(0, 0));
-/// ~~~~
+/// ```
 impl Default for NaiveDateTime {
     fn default() -> Self {
         NaiveDateTime::from_timestamp(0, 0)

src/naive/time.rs

@@ -1341,16 +1341,16 @@ impl str::FromStr for NaiveTime {
     }
 }
 
-/// The default for a NaiveTime is midnight, oo:oo:00 exactly.
+/// The default value for a NaiveTime is midnight, 00:00:00 exactly.
 ///
 /// # Example
 ///
-/// ~~~~
+/// ```rust
 /// use chrono::NaiveTime;
 ///
 /// let default_time = NaiveTime::default();
 /// assert_eq!(default_time, NaiveTime::from_hms(0, 0, 0));
-/// ~~~~
+/// ```
 impl Default for NaiveTime {
     fn default() -> Self {
         NaiveTime::from_hms(0, 0, 0)