diff --git a/crates/fidc-core/src/signal_contract.rs b/crates/fidc-core/src/signal_contract.rs
index 3c58ff7..445769a 100644
--- a/crates/fidc-core/src/signal_contract.rs
+++ b/crates/fidc-core/src/signal_contract.rs
@@ -422,13 +422,13 @@ mod tests {
         raw.snapshots[0].generated_at="2025-01-07T08:45:00+08:00".parse().unwrap();
         raw.snapshots[0].published_at="2025-01-07T08:46:00+08:00".parse().unwrap();
         let value=seal(raw).validate().unwrap();
-        for clock in ["2025-01-06 15:00:00", "2025-01-07 08:45:00"] {
+        for clock in ["2025-01-06T15:00:00", "2025-01-07T08:45:00"] {
             at_context(Some(clock.parse().unwrap()), |ctx| {
                 assert_eq!(value.intents(ctx).unwrap_err(),"observed_signal_published_after_consumption_clock");
                 assert!(ctx.portfolio.positions().is_empty());
             });
         }
-        at_context(Some("2025-01-07 09:30:00".parse().unwrap()), |ctx| {
+        at_context(Some("2025-01-07T09:30:00".parse().unwrap()), |ctx| {
             assert_eq!(value.intents(ctx).unwrap().len(),1);
             assert!(ctx.portfolio.positions().is_empty());
         });
@@ -438,8 +438,8 @@ mod tests {
     #[test]
     fn reconstruction_ignores_research_wall_clock_but_never_early_input_availability() {
         let value=book().validate().unwrap();
-        at_context(Some("2025-01-06 15:00:00".parse().unwrap()), |ctx| assert!(value.intents(ctx).is_ok()));
-        at_context(Some("2025-01-06 14:59:59".parse().unwrap()), |ctx| {
+        at_context(Some("2025-01-06T15:00:00".parse().unwrap()), |ctx| assert!(value.intents(ctx).is_ok()));
+        at_context(Some("2025-01-06T14:59:59".parse().unwrap()), |ctx| {
             assert_eq!(value.intents(ctx).unwrap_err(),"signal_not_available_at_consumption_clock");
         });
         let mut raw=book();
@@ -447,7 +447,7 @@ mod tests {
         raw.snapshots[0].input_available_at=raw.snapshots[0].input_as_of;
         raw.snapshots[0].signal_at=raw.snapshots[0].input_as_of;
         let value=seal(raw).validate().unwrap();
-        at_context(Some("2025-01-07 09:30:00".parse().unwrap()), |ctx| {
+        at_context(Some("2025-01-07T09:30:00".parse().unwrap()), |ctx| {
             assert_eq!(value.intents(ctx).unwrap_err(),"next_open_signal_contains_execution_session_inputs");
         });
     }