diff --git a/Cargo.lock b/Cargo.lock
index f02baf5..1be57a2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -756,6 +756,17 @@ dependencies = [
  "typenum",
 ]
 
+[[package]]
+name = "dimensioned"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a0b0a86c5d31c93238ff4b694fa31f3acdf67440770dc314c57d90e433914397"
+dependencies = [
+ "generic-array 0.14.7",
+ "num-traits",
+ "typenum",
+]
+
 [[package]]
 name = "displaydoc"
 version = "0.2.4"
@@ -807,7 +818,7 @@ version = "0.6.0"
 dependencies = [
  "chrono",
  "chrono-tz",
- "dimensioned",
+ "dimensioned 0.7.0",
  "serde 1.0.188",
  "serde_derive",
  "serde_json",
@@ -960,6 +971,15 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8fcfdc7a0362c9f4444381a9e697c79d435fe65b52a37466fc2c1184cee9edc6"
 
+[[package]]
+name = "fitnesstrax"
+version = "0.1.0"
+dependencies = [
+ "chrono",
+ "dimensioned 0.8.0",
+ "emseries",
+]
+
 [[package]]
 name = "flate2"
 version = "1.0.27"
diff --git a/Cargo.toml b/Cargo.toml
index 1957e1d..0aed9b0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ members = [
     "dashboard",
     "emseries",
     "file-service",
+    "fitnesstrax",
     "fluent-ergonomics",
     "geo-types",
     "gm-control-panel",
diff --git a/build.sh b/build.sh
index dcaed56..8311bd5 100755
--- a/build.sh
+++ b/build.sh
@@ -11,6 +11,7 @@ RUST_ALL_TARGETS=(
     "dashboard"
     "emseries"
     "file-service"
+    "fitnesstrax"
     "fluent-ergonomics"
     "geo-types"
     "gm-control-panel"
diff --git a/fitnesstrax/Cargo.toml b/fitnesstrax/Cargo.toml
new file mode 100644
index 0000000..da0b1bc
--- /dev/null
+++ b/fitnesstrax/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "fitnesstrax"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+chrono      = { version = "0.4" }
+dimensioned = {version = "0.8" }
+emseries    = { path = "../emseries" }
diff --git a/fitnesstrax/src/legacy.rs b/fitnesstrax/src/legacy.rs
new file mode 100644
index 0000000..0a79713
--- /dev/null
+++ b/fitnesstrax/src/legacy.rs
@@ -0,0 +1,24 @@
+use crate::types;
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn read_a_legacy_set_rep_record() {
+        unimplemented!()
+    }
+
+    #[test]
+    fn read_a_legacy_steps_record() {
+        unimplemented!()
+    }
+
+    #[test]
+    fn read_a_legacy_time_distance_record() {
+        unimplemented!()
+    }
+
+    #[test]
+    fn read_a_legacy_weight_record() {
+        unimplemented!()
+    }
+}
diff --git a/fitnesstrax/src/lib.rs b/fitnesstrax/src/lib.rs
new file mode 100644
index 0000000..b591639
--- /dev/null
+++ b/fitnesstrax/src/lib.rs
@@ -0,0 +1,6 @@
+use chrono::NaiveDate;
+use dimensioned::si;
+use emseries::DateTimeTz;
+
+mod legacy;
+mod types;
diff --git a/fitnesstrax/src/main.rs b/fitnesstrax/src/main.rs
new file mode 100644
index 0000000..e7a11a9
--- /dev/null
+++ b/fitnesstrax/src/main.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/fitnesstrax/src/types.rs b/fitnesstrax/src/types.rs
new file mode 100644
index 0000000..0dfc3e5
--- /dev/null
+++ b/fitnesstrax/src/types.rs
@@ -0,0 +1,59 @@
+/// SetRep represents workouts like pushups or situps, which involve doing a "set" of a number of
+/// actions, resting, and then doing another set.
+pub struct SetRep {
+    /// I assume that a set/rep workout is only done once in a day.
+    date: NaiveDate,
+    /// Each set entry represents the number of times that the action was performed in a set. So, a
+    /// pushup workout that involved five sets would have five entries. Each entry would be x
+    /// number of pushups. A viable workout would be something like [6, 6, 4, 4, 5].
+    sets: Vec<u32>,
+    comments: Option<String>,
+}
+
+/// The number of steps one takes in a single day.
+pub struct Steps {
+    date: NaiveDate,
+    count: u32,
+}
+
+/// TimeDistance represents workouts characterized by a duration and a distance travelled. These
+/// sorts of workouts can occur many times a day, depending on how one records things. I might
+/// record a single 30-km workout if I go on a long-distanec ride. Or I might record multiple 5km
+/// workouts if I am out running errands. Distance and Duration are both optional because different
+/// people have different priorities and may choose to measure different things.
+pub struct TimeDistance {
+    /// The precise time (and the relevant timezone) of the workout. One of the edge cases that I
+    /// account for is that a ride which occurred at 11pm in one timezone would then count as 1am
+    /// if one moved two timezones to the east. This is kind of nonsensical from a human
+    /// perspective, so the DateTimeTz keeps track of the precise time in UTC, but also the
+    /// timezone in which the event was recorded.
+    datetime: DateTimeTz,
+    /// The distance travelled. This is optional because such a workout makes sense even without
+    /// the distance.
+    distance: Option<si::Meter<f64>>,
+    /// The duration of the workout, which is also optional. Some people may keep track of the
+    /// amount of distance travelled without tracking the duration.
+    duration: Option<si::Second<f64>>,
+    comments: Option<String>,
+}
+
+/// A singular daily weight measurement. Weight changes slowly enough that it seems unlikely to
+/// need to track more than a single weight in a day.
+pub struct Weight {
+    date: NaiveDate,
+    weight: si::Kilogram<f64>,
+}
+
+/// The unified data structure for all records that are part of the app.
+pub enum TraxRecord {
+    BikeRide(TimeDistance),
+    Pushups,
+    Row(TimeDistance),
+    Run(TimeDistance),
+    Situps,
+    Squats,
+    Steps(Steps),
+    Swim(TimeDistance),
+    Walk(TimeDistance),
+    Weight(Weight),
+}