minor fix for UnixTimestamp

CHANGELOG.md

@@ -21,6 +21,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Added missing Service IDs to `ecss.PusServiceId` and marked in `#[non_exhaustive]`.
 
+## Fixed
+
+- `time.UnixTimestamp`: All constructors and `From` conversions now use the `new` constructor,
+  which should cause a correct conversion of 0 subsecond milliseconds to a `None` value.
+
 # [v0.5.2] 2023-01-26
 
 ## Added

src/time/mod.rs

@@ -285,10 +285,7 @@ impl UnixTimestamp {
     pub fn from_now() -> Result<Self, SystemTimeError> {
         let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
         let epoch = now.as_secs();
-        Ok(UnixTimestamp {
-            unix_seconds: epoch as i64,
-            subsecond_millis: Some(now.subsec_millis() as u16),
-        })
+        Ok(Self::const_new(epoch as i64, now.subsec_millis() as u16))
     }
 
     #[inline]
@@ -310,10 +307,7 @@ impl UnixTimestamp {
 
 impl From<DateTime<Utc>> for UnixTimestamp {
     fn from(value: DateTime<Utc>) -> Self {
-        Self {
-            unix_seconds: value.timestamp(),
-            subsecond_millis: Some(value.timestamp_subsec_millis() as u16),
-        }
+        Self::const_new(value.timestamp(), value.timestamp_subsec_millis() as u16)
     }
 }