From f42ee77e318a44c7c8e37f5938fc47feaf132ef9 Mon Sep 17 00:00:00 2001
From: One <43485962+c-git@users.noreply.github.com>
Date: Wed, 5 Aug 2026 00:49:37 -0400
Subject: [PATCH 1/2] feat: add fallible version of date conversion

---
 src/helper/date.rs | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/helper/date.rs b/src/helper/date.rs
index 2e5d2136..dac01daa 100644
--- a/src/helper/date.rs
+++ b/src/helper/date.rs
@@ -157,6 +157,14 @@ pub fn excel_to_date_time_parts(excel_timestamp: f64) -> (jiff::civil::Date, i64
 /// The integer part of the timestamp represents the number of days since a base
 /// date, while the fractional part represents the time of day.
 ///
+/// The fallible version of this method is [`excel_to_date_time_jiff_checked`].
+///
+/// # Panics
+///
+/// This panics when the input causes the number of days since the `base_date`
+/// to be outside of the supported range for `jiff` spans. See
+/// [`jiff::Span::days`] for relevant bounds.
+///
 /// # Parameters
 ///
 /// - `excel_timestamp: f64` The Excel timestamp to be converted and it is
@@ -191,10 +199,25 @@ pub fn excel_to_date_time_parts(excel_timestamp: f64) -> (jiff::civil::Date, i64
 /// ```
 #[must_use]
 pub fn excel_to_date_time_jiff(excel_timestamp: f64) -> jiff::civil::DateTime {
+    excel_to_date_time_jiff_checked(excel_timestamp).expect("input was out of supported range")
+}
+
+/// This is the fallible version of [`excel_to_date_time_jiff`]. See
+/// documentation on that function.
+///
+/// # Error
+///
+/// This returns an error when the input causes the number of days since the
+/// `base_date` to be outside of the supported range for `jiff` spans. See
+/// [`jiff::Span::days`] for relevant bounds.
+pub fn excel_to_date_time_jiff_checked(
+    excel_timestamp: f64,
+) -> Result<jiff::civil::DateTime, jiff::Error> {
     let (base_date, days, time) = excel_to_date_time_parts(excel_timestamp);
-    let seconds: i64 = cast((time * (24.0 * 60.0 * 60.0)).round()).unwrap();
+    let seconds: i64 = cast((time * (24.0 * 60.0 * 60.0)).round())
+        .expect("this cast should never fail because `time` should be a value between 0 and 1");
 
-    base_date.at(0, 0, 0, 0) + days.day().seconds(seconds)
+    Ok(base_date.at(0, 0, 0, 0) + jiff::Span::new().try_days(days)?.seconds(seconds))
 }
 
 /// Converts an Excel timestamp to a [`jiff::civil::DateTime`] object with
@@ -691,4 +714,13 @@ mod tests {
             "chrono conversion is incorrect"
         );
     }
+
+    #[test]
+    fn excel_to_date_time_checked() {
+        let actual = excel_to_date_time_jiff_checked(123_456_789.0);
+        assert!(
+            actual.is_err(),
+            "Value is out of range of jiff::Span days and should be rejected"
+        );
+    }
 }

From 6832970876204f584f3f13d8ae82f8a21e90276b Mon Sep 17 00:00:00 2001
From: One <43485962+c-git@users.noreply.github.com>
Date: Wed, 5 Aug 2026 00:56:21 -0400
Subject: [PATCH 2/2] chore: address clippy lints

---
 src/helper/number_format/number_formater.rs     | 8 ++++----
 src/helper/number_format/percentage_formater.rs | 9 ++++++---
 src/structs/data_bar.rs                         | 2 +-
 tests/streaming_writer_test.rs                  | 4 ++++
 4 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/helper/number_format/number_formater.rs b/src/helper/number_format/number_formater.rs
index 29e20c25..c1912a67 100644
--- a/src/helper/number_format/number_formater.rs
+++ b/src/helper/number_format/number_formater.rs
@@ -344,7 +344,7 @@ mod tests {
     #[test]
     fn format_as_number_rounds_half_away_from_zero() {
         // Excel rounds display values; truncating turned 107310.6 into 107,310.
-        assert_eq!(format_as_number(107310.6, "#,##0"), "107,311");
+        assert_eq!(format_as_number(107_310.6, "#,##0"), "107,311");
         assert_eq!(format_as_number(12.5, "0"), "13");
         assert_eq!(format_as_number(-12.5, "0"), "-13");
         assert_eq!(format_as_number(99999.5, "0"), "100000");
@@ -371,13 +371,13 @@ mod tests {
     #[test]
     fn format_as_number_keeps_currency_prefix() {
         assert_eq!(format_as_number(39.1, "$0.00"), "$39.10");
-        assert_eq!(format_as_number(107310.6, "$#,##0"), "$107,311");
+        assert_eq!(format_as_number(107_310.6, "$#,##0"), "$107,311");
     }
 
     #[test]
     fn format_as_number_thousands_grouping_survives_rounding() {
-        assert_eq!(format_as_number(999999.5, "#,##0"), "1,000,000");
-        assert_eq!(format_as_number(1234567.891, "#,##0.00"), "1,234,567.89");
+        assert_eq!(format_as_number(999_999.5, "#,##0"), "1,000,000");
+        assert_eq!(format_as_number(1_234_567.891, "#,##0.00"), "1,234,567.89");
         assert_eq!(format_as_number(-1234.5, "#,##0"), "-1,235");
     }
 }
diff --git a/src/helper/number_format/percentage_formater.rs b/src/helper/number_format/percentage_formater.rs
index 4172d984..aa09a13a 100644
--- a/src/helper/number_format/percentage_formater.rs
+++ b/src/helper/number_format/percentage_formater.rs
@@ -51,12 +51,15 @@ mod tests {
     fn format_as_percentage_keeps_decimal_precision() {
         // Rounding to an integer before applying the decimal format code
         // turned 17.309...% into "17.0%".
-        assert_eq!(format_as_percentage(0.1730909090909091, "0.0%"), "17.3%");
+        assert_eq!(
+            format_as_percentage(0.173_090_909_090_909_1, "0.0%"),
+            "17.3%"
+        );
     }
 
     #[test]
     fn format_as_percentage_integer_format() {
-        assert_eq!(format_as_percentage(0.1730909090909091, "0%"), "17%");
+        assert_eq!(format_as_percentage(0.173_090_909_090_909_1, "0%"), "17%");
     }
 
     #[test]
@@ -71,6 +74,6 @@ mod tests {
         // display value (106.5) away from zero.
         assert_eq!(format_as_percentage(1.065, "0%"), "107%");
         assert_eq!(format_as_percentage(0.125, "0.0%"), "12.5%");
-        assert_eq!(format_as_percentage(0.10649999999999999, "0%"), "11%");
+        assert_eq!(format_as_percentage(0.106_499_999_999_999_99, "0%"), "11%");
     }
 }
diff --git a/src/structs/data_bar.rs b/src/structs/data_bar.rs
index 40121dd8..a5705ac8 100644
--- a/src/structs/data_bar.rs
+++ b/src/structs/data_bar.rs
@@ -137,7 +137,7 @@ mod tests {
         let mut buf = Vec::new();
         loop {
             match reader.read_event_into(&mut buf) {
-                Ok(Event::Start(ref e)) | Ok(Event::Empty(ref e))
+                Ok(Event::Start(ref e) | Event::Empty(ref e))
                     if e.name().into_inner() == b"dataBar" =>
                 {
                     let mut obj = DataBar::default();
diff --git a/tests/streaming_writer_test.rs b/tests/streaming_writer_test.rs
index aae9a3de..a746be97 100644
--- a/tests/streaming_writer_test.rs
+++ b/tests/streaming_writer_test.rs
@@ -32,6 +32,10 @@ use umya_spreadsheet::{
 /// intentionally non-ASCII to exercise UTF-8 handling in workbook.xml.
 const SHEETS: [&str; 3] = ["Sheet1", "Sheet2", "データ"];
 
+#[expect(
+    clippy::approx_constant,
+    reason = "used in a test and not worth changing"
+)]
 /// Build a deterministic, multi-sheet workbook covering the common cell value
 /// kinds (string, number, bool, formula) plus a non-ASCII string value.
 fn build_book() -> Workbook {