Use instant for Time::now() (#2090)

crates/re_log_types/Cargo.toml

@@ -65,6 +65,7 @@ document-features = "0.2"
 fixed = { version = "1.17", default-features = false, features = ["serde"] }
 half = { workspace = true, features = ["bytemuck"] }
 itertools = { workspace = true }
+instant = { version = "0.1" }
 lazy_static.workspace = true
 ndarray.workspace = true
 nohash-hasher = "0.2"

crates/re_log_types/src/time.rs

@@ -7,10 +7,9 @@ use time::OffsetDateTime;
 pub struct Time(i64);
 
 impl Time {
-    #[cfg(not(target_arch = "wasm32"))]
     #[inline]
     pub fn now() -> Self {
-        let nanos_since_epoch = std::time::SystemTime::UNIX_EPOCH
+        let nanos_since_epoch = instant::SystemTime::UNIX_EPOCH
             .elapsed()
             .expect("Expected system clock to be set to after 1970")
             .as_nanos() as _;
@@ -156,6 +155,18 @@ impl TryFrom<std::time::SystemTime> for Time {
     }
 }
 
+// On non-wasm32 builds, `instant::SystemTime` is a re-export of `std::time::SystemTime`,
+// so it's covered by the above `TryFrom`.
+#[cfg(target_arch = "wasm32")]
+impl TryFrom<instant::SystemTime> for Time {
+    type Error = ();
+
+    fn try_from(time: instant::SystemTime) -> Result<Time, Self::Error> {
+        time.duration_since(instant::SystemTime::UNIX_EPOCH)
+            .map(|duration_since_epoch| Time(duration_since_epoch.as_nanos() as _))
+    }
+}
+
 impl TryFrom<time::OffsetDateTime> for Time {
     type Error = core::num::TryFromIntError;