Groundwork: widen year parsing bounds for GNU max year

src/items/builder.rs

@@ -221,7 +221,9 @@ impl DateTimeBuilder {
             let d: civil::Date = if date.year.is_some() {
                 date.try_into()?
             } else {
-                date.with_year(dt.date().year() as u16).try_into()?
+                let base_year = u32::try_from(dt.date().year())
+                    .map_err(|_| "base year must be non-negative")?;
+                date.with_year(base_year).try_into()?
             };
             dt = dt.with().date(d).build()?;
         }

src/items/date.rs

@@ -44,11 +44,11 @@ use super::{
 pub(crate) struct Date {
     pub(crate) day: u8,
     pub(crate) month: u8,
-    pub(crate) year: Option<u16>,
+    pub(crate) year: Option<u32>,
 }
 
 impl Date {
-    pub(super) fn with_year(self, year: u16) -> Self {
+    pub(super) fn with_year(self, year: u32) -> Self {
         Date {
             day: self.day,
             month: self.month,
@@ -118,12 +118,12 @@ impl TryFrom<Date> for jiff::civil::Date {
     type Error = &'static str;
 
     fn try_from(date: Date) -> Result<Self, Self::Error> {
-        jiff::civil::Date::new(
-            date.year.unwrap_or(0) as i16,
-            date.month as i8,
-            date.day as i8,
-        )
-        .map_err(|_| "date is not valid")
+        let year = date.year.unwrap_or(0);
+        let year: i16 = year
+            .try_into()
+            .map_err(|_| "date year is outside the supported range")?;
+        jiff::civil::Date::new(year, date.month as i8, date.day as i8)
+            .map_err(|_| "date is not valid")
     }
 }
 

src/items/mod.rs

@@ -408,13 +408,9 @@ mod tests {
         let result = parse(&mut "2025-05-19 @1690466034");
         assert!(result.is_err());
 
-        // Pure number as year (too large).
+        // Pure number as year (large years are parsed successfully).
         let result = parse(&mut "jul 18 12:30 10000");
-        assert!(result.is_err());
-        assert!(result
-            .unwrap_err()
-            .to_string()
-            .contains("year must be no greater than 9999"));
+        assert!(result.is_ok());
 
         // Pure number as time (too long).
         let result = parse(&mut "01:02 12345");
@@ -449,6 +445,20 @@ mod tests {
             .contains("invalid minute in pure number"));
     }
 
+    #[test]
+    fn negative_base_year_with_yearless_date_errors() {
+        let base = DateTime::new(-1, 1, 1, 0, 0, 0, 0)
+            .unwrap()
+            .to_zoned(TimeZone::UTC)
+            .unwrap();
+        let result = parse_at_date(base, "11/14");
+        assert!(result.is_err());
+        assert!(result
+            .unwrap_err()
+            .to_string()
+            .contains("base year must be non-negative"));
+    }
+
     #[test]
     fn relative_weekday() {
         // Jan 1 2025 is a Wed

src/items/year.rs

@@ -14,11 +14,14 @@ use winnow::{stream::AsChar, token::take_while, ModalResult, Parser};
 
 use super::primitive::s;
 
+const GNU_MAX_YEAR: u32 = 2_147_485_547;
+const GNU_MAX_YEAR_ERROR: &str = "year exceeds GNU maximum";
+
 // TODO: Leverage `TryFrom` trait.
-pub(super) fn year_from_str(year_str: &str) -> Result<u16, &'static str> {
+pub(super) fn year_from_str(year_str: &str) -> Result<u32, &'static str> {
     let mut year = year_str
-        .parse::<u16>()
-        .map_err(|_| "year must be a valid u16 number")?;
+        .parse::<u32>()
+        .map_err(|_| "year must be a non-negative integer")?;
 
     // If year is 68 or smaller, then 2000 is added to it; otherwise, if year
     // is less than 100, then 1900 is added to it.
@@ -34,13 +37,8 @@ pub(super) fn year_from_str(year_str: &str) -> Result<u16, &'static str> {
         }
     }
 
-    // 2147485547 is the maximum value accepted by GNU, but chrono only
-    // behaves like GNU for years in the range: [0, 9999], so we keep in the
-    // range [0, 9999].
-    //
-    // See discussion in https://github.com/uutils/parse_datetime/issues/160.
-    if year > 9999 {
-        return Err("year must be no greater than 9999");
+    if year > GNU_MAX_YEAR {
+        return Err(GNU_MAX_YEAR_ERROR);
     }
 
     Ok(year)
@@ -57,18 +55,31 @@ mod tests {
     #[test]
     fn test_year() {
         // 2-characters are converted to 19XX/20XX
-        assert_eq!(year_from_str("10").unwrap(), 2010u16);
-        assert_eq!(year_from_str("68").unwrap(), 2068u16);
-        assert_eq!(year_from_str("69").unwrap(), 1969u16);
-        assert_eq!(year_from_str("99").unwrap(), 1999u16);
+        assert_eq!(year_from_str("10").unwrap(), 2010u32);
+        assert_eq!(year_from_str("68").unwrap(), 2068u32);
+        assert_eq!(year_from_str("69").unwrap(), 1969u32);
+        assert_eq!(year_from_str("99").unwrap(), 1999u32);
 
         // 3,4-characters are converted verbatim
-        assert_eq!(year_from_str("468").unwrap(), 468u16);
-        assert_eq!(year_from_str("469").unwrap(), 469u16);
-        assert_eq!(year_from_str("1568").unwrap(), 1568u16);
-        assert_eq!(year_from_str("1569").unwrap(), 1569u16);
+        assert_eq!(year_from_str("468").unwrap(), 468u32);
+        assert_eq!(year_from_str("469").unwrap(), 469u32);
+        assert_eq!(year_from_str("1568").unwrap(), 1568u32);
+        assert_eq!(year_from_str("1569").unwrap(), 1569u32);
 
-        // years greater than 9999 are not accepted
-        assert!(year_from_str("10000").is_err());
+        // very large years are accepted up to GNU's upper bound
+        assert_eq!(year_from_str("10000").unwrap(), 10000u32);
+        assert_eq!(year_from_str("2147485547").unwrap(), 2_147_485_547u32);
+        assert_eq!(
+            year_from_str("2147485548").unwrap_err(),
+            "year exceeds GNU maximum"
+        );
+    }
+
+    #[test]
+    fn test_year_errors() {
+        assert_eq!(
+            year_from_str("not-a-year").unwrap_err(),
+            "year must be a non-negative integer"
+        );
     }
 }