Add TimeZone::timestamp_micros

src/offset/mod.rs

@@ -431,6 +431,24 @@ pub trait TimeZone: Sized + Clone {
         self.timestamp_opt(secs, nanos as u32).unwrap()
     }
 
+    /// Makes a new `DateTime` from the number of non-leap microseconds
+    /// since January 1, 1970 0:00:00 UTC (aka "UNIX timestamp").
+    ///
+    /// #Example
+    /// ```
+    /// use chrono::{Utc, TimeZone};
+    ///
+    /// assert_eq!(Utc.timestamp_micros_opt(1431648000000).unwrap().timestamp(), 1431648);
+    /// ```
+    fn timestamp_micros_opt(&self, micros: i64) -> LocalResult<DateTime<Self>> {
+        let (mut secs, mut micros) = (micros / 1_000_000, micros % 1_000_000);
+        if micros < 0 {
+            secs -= 1;
+            micros += 1_000_000;
+        }
+        self.timestamp_opt(secs, (micros * 1000) as u32)
+    }
+
     /// Parses a string with the specified format string and returns a
     /// `DateTime` with the current offset.
     ///
@@ -556,4 +574,23 @@ mod tests {
         Utc.timestamp_nanos(i64::default());
         Utc.timestamp_nanos(i64::min_value());
     }
+
+    #[test]
+    fn test_negative_micros() {
+        let dt = Utc.timestamp_micros_opt(-1_000_000).unwrap();
+        assert_eq!(dt.to_string(), "1969-12-31 23:59:59 UTC");
+        let dt = Utc.timestamp_micros_opt(-999_999).unwrap();
+        assert_eq!(dt.to_string(), "1969-12-31 23:59:59.000001 UTC");
+        let dt = Utc.timestamp_micros_opt(-1).unwrap();
+        assert_eq!(dt.to_string(), "1969-12-31 23:59:59.999999 UTC");
+        let dt = Utc.timestamp_micros_opt(-60_000_000).unwrap();
+        assert_eq!(dt.to_string(), "1969-12-31 23:59:00 UTC");
+        let dt = Utc.timestamp_micros_opt(-3_600_000_000).unwrap();
+        assert_eq!(dt.to_string(), "1969-12-31 23:00:00 UTC");
+    }
+
+    #[test]
+    fn test_micros_example() {
+        assert_eq!(Utc.timestamp_micros_opt(1431648000000).unwrap().timestamp(), 1431648);
+    }
 }