diff --git a/src/store/day.rs b/src/store/day.rs
index b60f031..24c7f6c 100644
--- a/src/store/day.rs
+++ b/src/store/day.rs
@@ -3,7 +3,7 @@ use core::fmt::Write;
 use embedded_sdmmc::ShortFileName;
 use serde::{Deserialize, Serialize};
 
-#[derive(Clone, Copy, Serialize, Deserialize, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Serialize, Deserialize, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Day(u32);
 
 impl Day {