diff --git a/crates/ruma-common/src/lib.rs b/crates/ruma-common/src/lib.rs
index 873c9039..0626c8d4 100644
--- a/crates/ruma-common/src/lib.rs
+++ b/crates/ruma-common/src/lib.rs
@@ -13,3 +13,6 @@ pub mod presence;
 pub mod push;
 pub mod receipt;
 pub mod thirdparty;
+mod time;
+
+pub use time::{MilliSecondsSinceUnixEpoch, SecondsSinceUnixEpoch};
diff --git a/crates/ruma-common/src/time.rs b/crates/ruma-common/src/time.rs
new file mode 100644
index 00000000..d5443b4e
--- /dev/null
+++ b/crates/ruma-common/src/time.rs
@@ -0,0 +1,94 @@
+use js_int::UInt;
+use serde::{Deserialize, Serialize};
+use std::{
+    convert::TryInto,
+    time::{Duration, SystemTime, UNIX_EPOCH},
+};
+
+/// A timestamp represented as the number of milliseconds since the unix epoch.
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord, Deserialize, Serialize)]
+#[serde(transparent)]
+pub struct MilliSecondsSinceUnixEpoch(pub UInt);
+
+impl MilliSecondsSinceUnixEpoch {
+    /// Creates a `MilliSecondsSinceUnixEpoch` from the given `SystemTime`, if it is not before the
+    /// unix epoch, or too large to be represented.
+    pub fn from_system_time(time: SystemTime) -> Option<Self> {
+        let duration = time.duration_since(UNIX_EPOCH).ok()?;
+        let millis = duration.as_millis().try_into().ok()?;
+        Some(Self(millis))
+    }
+
+    /// The current milliseconds since the unix epoch.
+    pub fn now() -> Self {
+        Self::from_system_time(SystemTime::now()).unwrap()
+    }
+
+    /// Creates a `SystemTime` from `self`, if it can be represented.
+    pub fn to_system_time(self) -> Option<SystemTime> {
+        UNIX_EPOCH.checked_add(Duration::from_millis(self.0.into()))
+    }
+}
+
+/// A timestamp represented as the number of seconds since the unix epoch.
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord, Deserialize, Serialize)]
+#[serde(transparent)]
+pub struct SecondsSinceUnixEpoch(pub UInt);
+
+impl SecondsSinceUnixEpoch {
+    /// Creates a `MilliSecondsSinceUnixEpoch` from the given `SystemTime`, if it is not before the
+    /// unix epoch, or too large to be represented.
+    pub fn from_system_time(time: SystemTime) -> Option<Self> {
+        let duration = time.duration_since(UNIX_EPOCH).ok()?;
+        let millis = duration.as_secs().try_into().ok()?;
+        Some(Self(millis))
+    }
+
+    /// Creates a `SystemTime` from `self`, if it can be represented.
+    pub fn to_system_time(self) -> Option<SystemTime> {
+        UNIX_EPOCH.checked_add(Duration::from_secs(self.0.into()))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::time::{Duration, UNIX_EPOCH};
+
+    use js_int::uint;
+    use matches::assert_matches;
+    use serde::{Deserialize, Serialize};
+    use serde_json::json;
+
+    use super::{MilliSecondsSinceUnixEpoch, SecondsSinceUnixEpoch};
+
+    #[derive(Clone, Debug, Deserialize, Serialize)]
+    struct SystemTimeTest {
+        millis: MilliSecondsSinceUnixEpoch,
+        secs: SecondsSinceUnixEpoch,
+    }
+
+    #[test]
+    fn deserialize() {
+        let json = json!({ "millis": 3000, "secs": 60 });
+
+        assert_matches!(
+            serde_json::from_value::<SystemTimeTest>(json),
+            Ok(SystemTimeTest { millis, secs })
+            if millis.to_system_time() == Some(UNIX_EPOCH + Duration::from_millis(3000))
+                && secs.to_system_time() == Some(UNIX_EPOCH + Duration::from_secs(60))
+        );
+    }
+
+    #[test]
+    fn serialize() {
+        let request = SystemTimeTest {
+            millis: MilliSecondsSinceUnixEpoch::from_system_time(UNIX_EPOCH + Duration::new(2, 0))
+                .unwrap(),
+            secs: SecondsSinceUnixEpoch(uint!(0)),
+        };
+        assert_matches!(
+            serde_json::to_value(&request),
+            Ok(value) if value == json!({ "millis": 2000, "secs": 0 })
+        );
+    }
+}