diff --git a/src/format/mod.rs b/src/format/mod.rs
index 1cc5048c16..22b2723af4 100644
--- a/src/format/mod.rs
+++ b/src/format/mod.rs
@@ -519,7 +519,7 @@ fn format_inner<'a>(
             };
 
             if let Some(v) = v {
-                if (spec == &Year || spec == &IsoYear) && !(0 <= v && v < 10_000) {
+                if (spec == &Year || spec == &IsoYear) && !(0..10_000).contains(&v) {
                     // non-four-digit years require an explicit sign as per ISO 8601
                     match *pad {
                         Pad::None => write!(result, "{:+}", v),
diff --git a/src/format/parsed.rs b/src/format/parsed.rs
index b8ed2d90f2..c919cb7995 100644
--- a/src/format/parsed.rs
+++ b/src/format/parsed.rs
@@ -261,7 +261,7 @@ impl Parsed {
     /// given hour number in 12-hour clocks.
     #[inline]
     pub fn set_hour12(&mut self, value: i64) -> ParseResult<()> {
-        if value < 1 || value > 12 {
+        if !(1..=12).contains(&value) {
             return Err(OUT_OF_RANGE);
         }
         set_if_consistent(&mut self.hour_mod_12, value as u32 % 12)
diff --git a/src/format/scan.rs b/src/format/scan.rs
index 0efb1ee3d1..632fd31126 100644
--- a/src/format/scan.rs
+++ b/src/format/scan.rs
@@ -48,7 +48,7 @@ pub fn number(s: &str, min: usize, max: usize) -> ParseResult<(&str, i64)> {
     let mut n = 0i64;
     for (i, c) in bytes.iter().take(max).cloned().enumerate() {
         // cloned() = copied()
-        if c < b'0' || b'9' < c {
+        if !(b'0'..=b'9').contains(&c) {
             if i < min {
                 return Err(INVALID);
             } else {
@@ -79,7 +79,7 @@ pub fn nanosecond(s: &str) -> ParseResult<(&str, i64)> {
     let v = v.checked_mul(SCALE[consumed]).ok_or(OUT_OF_RANGE)?;
 
     // if there are more than 9 digits, skip next digits.
-    let s = s.trim_left_matches(|c: char| '0' <= c && c <= '9');
+    let s = s.trim_left_matches(|c: char| ('0'..='9').contains(&c));
 
     Ok((s, v))
 }
diff --git a/src/naive/date.rs b/src/naive/date.rs
index bfb94b497a..8887e9f1f8 100644
--- a/src/naive/date.rs
+++ b/src/naive/date.rs
@@ -1640,7 +1640,7 @@ impl fmt::Debug for NaiveDate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let year = self.year();
         let mdf = self.mdf();
-        if 0 <= year && year <= 9999 {
+        if (0..=9999).contains(&year) {
             write!(f, "{:04}-{:02}-{:02}", year, mdf.month(), mdf.day())
         } else {
             // ISO 8601 requires the explicit sign for out-of-range years
diff --git a/src/naive/isoweek.rs b/src/naive/isoweek.rs
index 7e34313bad..3de0b17c3d 100644
--- a/src/naive/isoweek.rs
+++ b/src/naive/isoweek.rs
@@ -131,7 +131,7 @@ impl fmt::Debug for IsoWeek {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let year = self.year();
         let week = self.week();
-        if 0 <= year && year <= 9999 {
+        if (0..=9999).contains(&year) {
             write!(f, "{:04}-W{:02}", year, week)
         } else {
             // ISO 8601 requires the explicit sign for out-of-range years
diff --git a/src/naive/time.rs b/src/naive/time.rs
index 4d2b5c2f51..8e0dc6fcd6 100644
--- a/src/naive/time.rs
+++ b/src/naive/time.rs
@@ -578,7 +578,7 @@ impl NaiveTime {
             secs += 1;
         }
         debug_assert!(-86_400 <= secs && secs < 2 * 86_400);
-        debug_assert!(0 <= frac && frac < 1_000_000_000);
+        debug_assert!((0..=1_000_000_000).contains(&frac));
 
         if secs < 0 {
             secs += 86_400;
@@ -587,7 +587,7 @@ impl NaiveTime {
             secs -= 86_400;
             morerhssecs += 86_400;
         }
-        debug_assert!(0 <= secs && secs < 86_400);
+        debug_assert!((0..=86_400).contains(&secs));
 
         (NaiveTime { secs: secs as u32, frac: frac as u32 }, morerhssecs)
     }