Add DateTime::local_unix_epoch (#4479)

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## Unreleased
 
 - Components
+  - `icu_calendar`
+    - New `DateTime::local_unix_epoch()` convenience constructor (https://github.com/unicode-org/icu4x/pull/4479)
   - `icu_properties`
     - Add `Aran` script code (https://github.com/unicode-org/icu4x/pull/4426)
 - Data model and providers

components/calendar/src/iso.rs

@@ -286,6 +286,15 @@ impl DateTime<Iso> {
         })
     }
 
+    /// Constructs an ISO datetime representing the UNIX epoch on January 1, 1970
+    /// at midnight.
+    pub fn local_unix_epoch() -> Self {
+        DateTime {
+            date: Date::unix_epoch(),
+            time: types::Time::midnight(),
+        }
+    }
+
     /// Minute count representation of calendars starting from 00:00:00 on Jan 1st, 1970.
     ///
     /// ```rust

ffi/capi/src/datetime.rs

@@ -55,6 +55,13 @@ pub mod ffi {
             Box::new(ICU4XIsoDateTime(dt))
         }
 
+        /// Creates a new [`ICU4XIsoDateTime`] of midnight on January 1, 1970
+        #[diplomat::rust_link(icu::calendar::DateTime::local_unix_epoch, FnInStruct)]
+        pub fn local_unix_epoch() -> Box<ICU4XIsoDateTime> {
+            let dt = DateTime::local_unix_epoch();
+            Box::new(ICU4XIsoDateTime(dt))
+        }
+
         /// Construct from the minutes since the local unix epoch for this date (Jan 1 1970, 00:00)
         #[diplomat::rust_link(
             icu::calendar::DateTime::from_minutes_since_local_unix_epoch,