More documentation for dates before 1 BCE or after 9999 CE

src/format/mod.rs

@@ -99,7 +99,7 @@ pub enum Pad {
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub enum Numeric {
     /// Full Gregorian year (FW=4, PW=∞).
-    /// May accept years before 1 BCE or after 9999 CE, given an initial sign.
+    /// May accept years before 1 BCE or after 9999 CE, given an initial sign (+/-).
     Year,
     /// Gregorian year divided by 100 (century number; FW=PW=2). Implies the non-negative year.
     YearDiv100,

src/format/strftime.rs

@@ -11,7 +11,7 @@ The following specifiers are available both to formatting and parsing.
 | Spec. | Example  | Description                                                                |
 |-------|----------|----------------------------------------------------------------------------|
 |       |          | **DATE SPECIFIERS:**                                                       |
-| `%Y`  | `2001`   | The full proleptic Gregorian year, zero-padded to 4 digits. chrono supports years from -262144 to 262143. |
+| `%Y`  | `2001`   | The full proleptic Gregorian year, zero-padded to 4 digits. chrono supports years from -262144 to 262143. Note: years before 1 BCE or after 9999 CE, require an initial sign (+/-).|
 | `%C`  | `20`     | The proleptic Gregorian year divided by 100, zero-padded to 2 digits. [^1] |
 | `%y`  | `01`     | The proleptic Gregorian year modulo 100, zero-padded to 2 digits. [^1]     |
 |       |          |                                                                            |

src/naive/datetime/mod.rs

@@ -308,6 +308,16 @@ impl NaiveDateTime {
     /// assert!(parse_from_str("2001-09-09 01:46:39 = UNIX timestamp 999999999", fmt).is_ok());
     /// assert!(parse_from_str("1970-01-01 00:00:00 = UNIX timestamp 1", fmt).is_err());
     /// ```
+    ///
+    /// Years before 1 BCE or after 9999 CE, require an initial sign
+    ///
+    ///```
+    /// # use chrono::{NaiveDate, NaiveDateTime};
+    /// # let parse_from_str = NaiveDateTime::parse_from_str;
+    /// let fmt = "%Y-%m-%d %H:%M:%S";
+    /// assert!(parse_from_str("10000-09-09 01:46:39", fmt).is_err());
+    /// assert!(parse_from_str("+10000-09-09 01:46:39", fmt).is_ok());
+    ///```     
     pub fn parse_from_str(s: &str, fmt: &str) -> ParseResult<NaiveDateTime> {
         let mut parsed = Parsed::new();
         parse(&mut parsed, s, StrftimeItems::new(fmt))?;