diff --git a/src/header/common/if_modified_since.rs b/src/header/common/if_modified_since.rs
new file mode 100644
index 00000000..8b2d60c4
--- /dev/null
+++ b/src/header/common/if_modified_since.rs
@@ -0,0 +1,42 @@
+use std::fmt::{mod, Show};
+use std::str::FromStr;
+use time::Tm;
+use header::{Header, HeaderFormat};
+use super::util::{from_one_raw_str, tm_from_str};
+
+/// The `If-Modified-Since` header field.
+#[deriving(PartialEq, Clone)]
+pub struct IfModifiedSince(pub Tm);
+
+deref!(IfModifiedSince -> Tm)
+
+impl Header for IfModifiedSince {
+    fn header_name(_: Option<IfModifiedSince>) -> &'static str {
+        "If-Modified-Since"
+    }
+
+    fn parse_header(raw: &[Vec<u8>]) -> Option<IfModifiedSince> {
+        from_one_raw_str(raw)
+    }
+}
+
+
+impl HeaderFormat for IfModifiedSince {
+    fn fmt_header(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let tm = **self;
+        match tm.tm_utcoff {
+            0 => tm.rfc822().fmt(fmt),
+            _ => tm.to_utc().rfc822().fmt(fmt)
+        }
+    }
+}
+
+impl FromStr for IfModifiedSince {
+    fn from_str(s: &str) -> Option<IfModifiedSince> {
+        tm_from_str(s).map(IfModifiedSince)
+    }
+}
+
+bench_header!(imf_fixdate, IfModifiedSince, { vec![b"Sun, 07 Nov 1994 08:48:37 GMT".to_vec()] })
+bench_header!(rfc_850, IfModifiedSince, { vec![b"Sunday, 06-Nov-94 08:49:37 GMT".to_vec()] })
+bench_header!(asctime, IfModifiedSince, { vec![b"Sun Nov  6 08:49:37 1994".to_vec()] })
diff --git a/src/header/common/mod.rs b/src/header/common/mod.rs
index 0faca3c3..38476925 100644
--- a/src/header/common/mod.rs
+++ b/src/header/common/mod.rs
@@ -102,6 +102,9 @@ pub mod host;
 /// Exposes the LastModified header.
 pub mod last_modified;
 
+/// Exposes the If-Modified-Since header.
+pub mod if_modified_since;
+
 /// Exposes the Location header.
 pub mod location;