Fix Weekday calculation to skip using TimeZone when converting DateTime to timestamp, so that the calculated weekday will match local time rather than UTC.

src/datetime.rs

@@ -24,8 +24,7 @@ impl DateTime {
         self.year.get()
     }
 
-    /// Gets the Unix timestamp corresponding to this `DateTime`
-    pub fn timestamp(&self) -> i64 {
+    fn timestamp_naive(&self) -> i64 {
         let mut seconds: i64 = 0;
         let mut year = Year::new(1970);
         if self.year() < 1970 {
@@ -50,6 +49,12 @@ impl DateTime {
         seconds += i64::from(self.hour) * SECONDS_PER_HOUR;
         seconds += i64::from(self.minute) * SECONDS_PER_MINUTE;
         seconds += i64::from(self.second);
+        seconds
+    }
+
+    /// Gets the Unix timestamp corresponding to this `DateTime`
+    pub fn timestamp(&self) -> i64 {
+        let mut seconds = self.timestamp_naive();
         seconds += self.zone.as_seconds();
         seconds
     }
@@ -141,7 +146,7 @@ impl DateTime {
     }
 
     pub fn weekday(&self) -> Weekday {
-        let ts = self.timestamp();
+        let ts = self.timestamp_naive();
         let days = ts / SECONDS_PER_DAY;
         let rem = days % 7;
         rem.try_into().unwrap()