refactor[rust]: simpler timezone cast (#5014)

pola-rs · Sep 28, 2022 · 6eb71ce · 6eb71ce
1 parent 2cf3d7b
commit 6eb71ce
Showing 1 changed file with 3 additions and 34 deletions.
diff --git a/polars/polars-time/src/chunkedarray/kernels.rs b/polars/polars-time/src/chunkedarray/kernels.rs
@@ -234,66 +234,35 @@ pub(crate) fn cast_timezone(
     to: chrono_tz::Tz,
 ) -> ArrayRef {
     use chrono::TimeZone;
-    use chrono_tz::OffsetComponents;
 
     match tu {
         TimeUnit::Milliseconds => Box::new(unary(
             arr,
             |value| {
                 let ndt = timestamp_ms_to_datetime(value);
-                // find the current offset from utc
                 let tz_aware = from.from_local_datetime(&ndt).unwrap();
-                let offset = tz_aware.offset();
-                let total_offset_from = offset.base_utc_offset() + offset.dst_offset();
-
-                // find the new offset from utc
                 let new_tz_aware = tz_aware.with_timezone(&to);
-                let offset = new_tz_aware.offset();
-                let total_offset_to = offset.base_utc_offset() + offset.dst_offset();
-                let offset = total_offset_to - total_offset_from;
-
-                // correct for that offset
-                (ndt + offset).timestamp_millis()
+                new_tz_aware.naive_local().timestamp_millis()
             },
             ArrowDataType::Int64,
         )),
         TimeUnit::Microseconds => Box::new(unary(
             arr,
             |value| {
                 let ndt = timestamp_us_to_datetime(value);
-                // find the current offset from utc
                 let tz_aware = from.from_local_datetime(&ndt).unwrap();
-                let offset = tz_aware.offset();
-                let total_offset_from = offset.base_utc_offset() + offset.dst_offset();
-
-                // find the new offset from utc
                 let new_tz_aware = tz_aware.with_timezone(&to);
-                let offset = new_tz_aware.offset();
-                let total_offset_to = offset.base_utc_offset() + offset.dst_offset();
-                let offset = total_offset_to - total_offset_from;
-
-                // correct for that offset
-                (ndt + offset).timestamp_micros()
+                new_tz_aware.naive_local().timestamp_micros()
             },
             ArrowDataType::Int64,
         )),
         TimeUnit::Nanoseconds => Box::new(unary(
             arr,
             |value| {
                 let ndt = timestamp_ns_to_datetime(value);
-                // find the current offset from utc
                 let tz_aware = from.from_local_datetime(&ndt).unwrap();
-                let offset = tz_aware.offset();
-                let total_offset_from = offset.base_utc_offset() + offset.dst_offset();
-
-                // find the new offset from utc
                 let new_tz_aware = tz_aware.with_timezone(&to);
-                let offset = new_tz_aware.offset();
-                let total_offset_to = offset.base_utc_offset() + offset.dst_offset();
-                let offset = total_offset_to - total_offset_from;
-
-                // correct for that offset
-                (ndt + offset).timestamp_nanos()
+                new_tz_aware.naive_local().timestamp_nanos()
             },
             ArrowDataType::Int64,
         )),