diff --git a/src/main.rs b/src/main.rs
index 6a0283f..ed197f9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@
 mod args;
 mod config;
 mod id;
+mod primitive;
 mod server;
 mod shared;
 mod somehow;
diff --git a/src/primitive.rs b/src/primitive.rs
new file mode 100644
index 0000000..5030cdf
--- /dev/null
+++ b/src/primitive.rs
@@ -0,0 +1,49 @@
+//! Primitive serializable and deserializable types.
+
+use serde::de;
+use serde_repr::{Deserialize_repr, Serialize_repr};
+use time::{format_description::well_known::Rfc3339, OffsetDateTime};
+
+/// The source of a line of output.
+#[derive(Clone, Serialize_repr, Deserialize_repr, sqlx::Type)]
+#[repr(u8)]
+pub enum Source {
+    Internal = 0,
+    Stdout = 1,
+    Stderr = 2,
+}
+
+/// The direction a measured value improves in.
+#[derive(Clone, Serialize_repr, Deserialize_repr, sqlx::Type)]
+#[repr(i8)]
+pub enum Direction {
+    LessIsBetter = -1,
+    Neutral = 0,
+    MoreIsBetter = 1,
+}
+
+/// A time stamp, usually formatted using RFC3339.
+#[derive(Clone, Copy, sqlx::Type)]
+#[sqlx(transparent)]
+pub struct Timestamp(pub OffsetDateTime);
+
+impl serde::Serialize for Timestamp {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        self.0.format(&Rfc3339).unwrap().serialize(serializer)
+    }
+}
+
+impl<'de> serde::Deserialize<'de> for Timestamp {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let input: &str = serde::Deserialize::deserialize(deserializer)?;
+        OffsetDateTime::parse(input, &Rfc3339)
+            .map_err(de::Error::custom)
+            .map(Self)
+    }
+}
diff --git a/src/server/workers.rs b/src/server/workers.rs
index 432c739..5c7d08d 100644
--- a/src/server/workers.rs
+++ b/src/server/workers.rs
@@ -5,7 +5,8 @@ use time::OffsetDateTime;
 use crate::{
     config::ServerConfig,
     id,
-    shared::{BenchMethod, Rfc3339Time, Run, UnfinishedRun, WorkerStatus},
+    primitive::Timestamp,
+    shared::{BenchMethod, Run, UnfinishedRun, WorkerStatus},
 };
 
 #[derive(Clone)]
@@ -84,7 +85,7 @@ impl Workers {
             id,
             hash,
             bench_method,
-            start: Rfc3339Time(OffsetDateTime::now_utc()),
+            start: Timestamp(OffsetDateTime::now_utc()),
         };
 
         // Reserve work so other workers don't choose it
diff --git a/src/shared.rs b/src/shared.rs
index 3300b41..bbc6420 100644
--- a/src/shared.rs
+++ b/src/shared.rs
@@ -2,55 +2,14 @@
 
 use std::{collections::HashMap, fmt};
 
-use serde::{de, Deserialize, Serialize};
-use serde_repr::{Deserialize_repr, Serialize_repr};
-use time::{format_description::well_known::Rfc3339, OffsetDateTime};
+use serde::{Deserialize, Serialize};
+
+use crate::primitive::{Source, Timestamp};
 
 fn is_false(b: &bool) -> bool {
     !b
 }
 
-#[derive(Clone, Copy)]
-pub struct Rfc3339Time(pub OffsetDateTime);
-
-impl serde::Serialize for Rfc3339Time {
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: serde::Serializer,
-    {
-        self.0.format(&Rfc3339).unwrap().serialize(serializer)
-    }
-}
-
-impl<'de> serde::Deserialize<'de> for Rfc3339Time {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: serde::Deserializer<'de>,
-    {
-        let input: &str = serde::Deserialize::deserialize(deserializer)?;
-        OffsetDateTime::parse(input, &Rfc3339)
-            .map_err(de::Error::custom)
-            .map(Self)
-    }
-}
-
-#[derive(Clone, Serialize_repr, Deserialize_repr, sqlx::Type)]
-#[repr(u8)]
-pub enum Source {
-    // TODO Internal = 0 ?
-    // Stdin would be fd 0
-    Stdout = 1,
-    Stderr = 2,
-}
-
-#[derive(Clone, Serialize_repr, Deserialize_repr, sqlx::Type)]
-#[repr(i8)]
-pub enum Direction {
-    LessIsBetter = -1,
-    Neutral = 0,
-    MoreIsBetter = 1,
-}
-
 #[derive(Clone, Serialize, Deserialize)]
 pub struct Measurement {
     pub value: f64,
@@ -81,7 +40,7 @@ pub struct Run {
     pub id: String,
     pub hash: String,
     pub bench_method: BenchMethod,
-    pub start: Rfc3339Time,
+    pub start: Timestamp,
 }
 
 #[derive(Clone, Serialize, Deserialize)]
@@ -89,7 +48,7 @@ pub struct UnfinishedRun {
     pub id: String,
     pub hash: String,
     pub bench_method: String,
-    pub start: Rfc3339Time,
+    pub start: Timestamp,
 
     #[serde(default)]
     pub last_output: Vec<(Source, String)>,
@@ -100,13 +59,13 @@ pub struct FinishedRun {
     pub id: String,
     pub hash: String,
     pub bench_method: String,
-    pub start: Rfc3339Time,
+    pub start: Timestamp,
 
     /// Override the server's end time.
     ///
     /// Should not be used in normal operation, but can be used when importing
     /// completed runs from other sources.
-    pub end: Option<Rfc3339Time>,
+    pub end: Option<Timestamp>,
 
     #[serde(default)]
     pub exit_code: i32,
diff --git a/src/worker/run.rs b/src/worker/run.rs
index 5f9916a..ea90372 100644
--- a/src/worker/run.rs
+++ b/src/worker/run.rs
@@ -10,7 +10,8 @@ use tokio::sync::Notify;
 
 use crate::{
     config::WorkerServerConfig,
-    shared::{BenchMethod, FinishedRun, Measurement, Run, Source, UnfinishedRun},
+    primitive::Source,
+    shared::{BenchMethod, FinishedRun, Measurement, Run, UnfinishedRun},
 };
 
 use super::server::Server;