diff --git a/crates/ruma-common/Cargo.toml b/crates/ruma-common/Cargo.toml
index 4f5b08f9..53cc55a5 100644
--- a/crates/ruma-common/Cargo.toml
+++ b/crates/ruma-common/Cargo.toml
@@ -23,6 +23,7 @@ server = []
 api = ["http", "thiserror"]
 compat = ["ruma-macros/compat", "ruma-identifiers-validation/compat"]
 events = ["indoc", "thiserror"]
+js = ["js-sys"]
 markdown = ["pulldown-cmark"]
 rand = ["rand_crate", "uuid"]
 unstable-exhaustive-types = []
@@ -65,6 +66,9 @@ url = "2.2.2"
 uuid = { version = "1.0.0", optional = true, features = ["v4"] }
 wildmatch = "2.0.0"
 
+[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dependencies]
+js-sys = { version = "0.3", optional = true }
+
 [dev-dependencies]
 assign = "1.1.1"
 http = "0.2.2"
diff --git a/crates/ruma-common/src/time.rs b/crates/ruma-common/src/time.rs
index 232da64d..f963dc37 100644
--- a/crates/ruma-common/src/time.rs
+++ b/crates/ruma-common/src/time.rs
@@ -23,7 +23,11 @@ impl MilliSecondsSinceUnixEpoch {
 
     /// The current system time in milliseconds since the unix epoch.
     pub fn now() -> Self {
-        Self::from_system_time(SystemTime::now()).unwrap()
+        #[cfg(not(all(target_arch = "wasm32", target_os = "unknown", feature = "js")))]
+        return Self::from_system_time(SystemTime::now()).unwrap();
+
+        #[cfg(all(target_arch = "wasm32", target_os = "unknown", feature = "js"))]
+        return Self(f64_to_uint(js_sys::Date::now()));
     }
 
     /// Creates a new `SystemTime` from `self`, if it can be represented.
@@ -59,7 +63,11 @@ impl SecondsSinceUnixEpoch {
 
     /// The current system-time as seconds since the unix epoch.
     pub fn now() -> Self {
-        Self::from_system_time(SystemTime::now()).unwrap()
+        #[cfg(not(all(target_arch = "wasm32", target_os = "unknown", feature = "js")))]
+        return Self::from_system_time(SystemTime::now()).unwrap();
+
+        #[cfg(all(target_arch = "wasm32", target_os = "unknown", feature = "js"))]
+        return Self(f64_to_uint(js_sys::Date::now() / 1000.0));
     }
 
     /// Creates a new `SystemTime` from `self`, if it can be represented.
@@ -73,6 +81,12 @@ impl SecondsSinceUnixEpoch {
     }
 }
 
+#[cfg(all(target_arch = "wasm32", target_os = "unknown", feature = "js"))]
+fn f64_to_uint(val: f64) -> UInt {
+    use std::convert::TryFrom;
+    UInt::try_from(val as u64).unwrap()
+}
+
 #[cfg(test)]
 mod tests {
     use std::time::{Duration, UNIX_EPOCH};