Add const fn none()

src/duration.rs

@@ -47,6 +47,9 @@ impl Duration {
     // TODO: duration_constants https://github.com/rust-lang/rust/issues/57391
     // TODO: div_duration https://github.com/rust-lang/rust/issues/63139
 
+    /// Returns a "none" value
+    pub const NONE: Self = Self(None);
+
     /// A duration of zero time.
     ///
     /// # Examples

src/instant.rs

@@ -60,6 +60,9 @@ use super::{pair_and_then, Duration, TryFromTimeError};
 pub struct Instant(Option<time::Instant>);
 
 impl Instant {
+    /// Returns a "none" value
+    pub const NONE: Self = Self(None);
+
     /// Returns an instant corresponding to "now".
     ///
     /// # Examples

tests/duration.rs

@@ -5,6 +5,11 @@ use core::time;
 
 use easytime::Duration;
 
+#[test]
+fn none() {
+    assert!(Duration::NONE.is_none());
+}
+
 #[test]
 fn cmp() {
     assert!(Duration::from_secs(1) == Duration::from_secs(1));

tests/instant.rs

@@ -21,6 +21,11 @@ pub mod std_tests {
         }};
     }
 
+    #[test]
+    fn none() {
+        assert!(Instant::NONE.is_none());
+    }
+
     #[test]
     fn instant_monotonic() {
         let a = Instant::now();