diff --git a/src/builtins/core/instant.rs b/src/builtins/core/instant.rs
index 41d49d7e8..86b959e09 100644
--- a/src/builtins/core/instant.rs
+++ b/src/builtins/core/instant.rs
@@ -17,7 +17,7 @@ use crate::{
     provider::TimeZoneProvider,
     rounding::{IncrementRounder, Round},
     time::EpochNanoseconds,
-    TemporalError, TemporalResult, TemporalUnwrap, TimeZone,
+    Calendar, TemporalError, TemporalResult, TemporalUnwrap, TimeZone,
 };
 
 use ixdtf::parsers::records::UtcOffsetRecordOrZ;
@@ -236,8 +236,8 @@ impl Instant {
     }
 
     // TODO: May end up needing a provider API during impl
-    pub fn to_zoned_date_time_iso(&self, _time_zone: TimeZone) -> TemporalResult<ZonedDateTime> {
-        Err(TemporalError::general("Not yet implemented"))
+    pub fn to_zoned_date_time_iso(&self, time_zone: TimeZone) -> ZonedDateTime {
+        ZonedDateTime::new_unchecked(*self, Calendar::default(), time_zone)
     }
 }