diff --git a/src/date.rs b/src/date.rs
index 80e964f033..f1cfdaf1a7 100644
--- a/src/date.rs
+++ b/src/date.rs
@@ -751,6 +751,10 @@ mod tests {
         assert_eq!(DateZ::from_ymd(0,     3, 4).to_string(),  "0000-03-04".to_string());
         assert_eq!(DateZ::from_ymd(-307,  3, 4).to_string(), "-0307-03-04".to_string());
         assert_eq!(DateZ::from_ymd(12345, 3, 4).to_string(), "+12345-03-04".to_string());
+
+        // the format specifier should have no effect on `TimeZ`
+        assert_eq!(format!("{:+30}", DateZ::from_ymd(1234, 5, 6)), "1234-05-06".to_string());
+        assert_eq!(format!("{:30}", DateZ::from_ymd(12345, 6, 7)), "+12345-06-07".to_string());
     }
 }
 
diff --git a/src/duration.rs b/src/duration.rs
index 5658adaa35..4d9493aabc 100644
--- a/src/duration.rs
+++ b/src/duration.rs
@@ -255,7 +255,7 @@ impl fmt::Show for Duration {
         let hasdate = self.days != 0;
         let hastime = (self.secs != 0 || self.nanos != 0) || !hasdate;
 
-        try!('P'.fmt(f));
+        try!(write!(f, "P"));
         if hasdate {
             // technically speaking the negative part is not the valid ISO 8601,
             // but we need to print it anyway.
@@ -344,6 +344,10 @@ mod tests {
         assert_eq!(Duration::nanoseconds(42).to_string(), "PT0,000000042S".to_string());
         assert_eq!((Duration::days(7) + Duration::milliseconds(6543)).to_string(),
                    "P7DT6,543S".to_string());
+
+        // the format specifier should have no effect on `Duration`
+        assert_eq!(format!("{:30}", Duration::days(1) + Duration::milliseconds(2345)),
+                   "P1DT2,345S".to_string());
     }
 }
 
diff --git a/src/time.rs b/src/time.rs
index ff90952ab2..84b235d455 100644
--- a/src/time.rs
+++ b/src/time.rs
@@ -332,6 +332,10 @@ mod tests {
                    "00:00:00,043210".to_string());
         assert_eq!(TimeZ::from_hms_nano(0, 0, 0, 6543210).to_string(),
                    "00:00:00,006543210".to_string());
+
+        // the format specifier should have no effect on `TimeZ`
+        assert_eq!(format!("{:30}", TimeZ::from_hms_milli(3, 5, 7, 9)),
+                   "03:05:07,009".to_string());
     }
 }