Repository: chronotope/chrono (language: rust)

Issue:
Century cutoff for %y undocumented
If I run
```rust
use chrono::NaiveDate;


fn main() {
    let res = NaiveDate::parse_from_str("01-01-69", "%d-%m-%y");
    println!("res: {:?}", res);
    let res = NaiveDate::parse_from_str("01-01-70", "%d-%m-%y");
    println!("res: {:?}", res);
}
```
I get
```
res: Ok(2069-01-01)
res: Ok(1970-01-01)
```

It seems that 70 is the cutoff, but the docs don't mention it https://docs.rs/chrono/latest/chrono/format/strftime/index.html#fn1


Discussion / hints:

Fix patch:
diff --git a/src/format/strftime.rs b/src/format/strftime.rs
index 555e36f9c0..e446c68c02 100644
--- a/src/format/strftime.rs
+++ b/src/format/strftime.rs
@@ -99,6 +99,8 @@ Notes:
 
 [^1]: `%C`, `%y`:
    This is floor division, so 100 BCE (year number -99) will print `-1` and `99` respectively.
+   For `%y`, values greater or equal to 70 are interpreted as being in the 20th century,
+   values smaller than 70 in the 21st century.
 
 [^2]: `%U`:
    Week 1 starts with the first Sunday in that year.


Test patch: