refactor: replace chrono with time-rs

src/util/date.rs

@@ -0,0 +1,44 @@
+use time::{Date, Month};
+
+pub const fn month_from_n(n: u8) -> Option<Month> {
+    match n {
+        1 => Some(Month::January),
+        2 => Some(Month::February),
+        3 => Some(Month::March),
+        4 => Some(Month::April),
+        5 => Some(Month::May),
+        6 => Some(Month::June),
+        7 => Some(Month::July),
+        8 => Some(Month::August),
+        9 => Some(Month::September),
+        10 => Some(Month::October),
+        11 => Some(Month::November),
+        12 => Some(Month::December),
+        _ => None,
+    }
+}
+
+/// Shift a date by the given number of months.
+/// Ambiguous month-ends are shifted backwards as necessary.
+pub fn shift_months(date: Date, months: i32) -> Date {
+    let mut year = date.year() + (date.month() as i32 + months) / 12;
+    let mut month = (date.month() as i32 + months) % 12;
+    let mut day = date.day();
+
+    if month < 1 {
+        year -= 1;
+        month += 12;
+    }
+
+    let month = month_from_n(month as u8).unwrap();
+    let month_days = time::util::days_in_year_month(year, month);
+
+    day = day.min(month_days);
+    Date::from_calendar_date(year, month, day).unwrap()
+}
+
+/// Shift a date by the given number of years.
+/// Ambiguous month-ends are shifted backwards as necessary.
+pub fn shift_years(date: Date, years: i32) -> Date {
+    shift_months(date, years * 12)
+}

src/util/mod.rs

@@ -1,7 +1,9 @@
+mod date;
 mod protobuf;
 
 pub mod dictionary;
 
+pub use date::{month_from_n, shift_months, shift_years};
 pub use protobuf::ProtoBuilder;
 
 use std::{