diff --git a/Cargo.lock b/Cargo.lock
index cf8a68c..59da77e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,92 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "autocfg"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
+
+[[package]]
+name = "chrono"
+version = "0.4.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
+dependencies = [
+ "libc",
+ "num-integer",
+ "num-traits",
+ "time",
+ "winapi",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.106"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a60553f9a9e039a333b4e9b20573b9e9b9c0bb3a11e201ccc48ef4283456d673"
+
+[[package]]
+name = "num-integer"
+version = "0.1.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2cc698a63b549a70bc047073d2949cce27cd1c7b0a4a862d08a8031bc2801db"
+dependencies = [
+ "autocfg",
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a64b1ec5cda2586e284722486d802acf1f7dbdc623e2bfc57e65ca1cd099290"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "time"
+version = "0.1.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db9e6914ab8b1ae1c260a4ae7a49b6c5611b40328a735b21862567685e73255"
+dependencies = [
+ "libc",
+ "wasi",
+ "winapi",
+]
+
 [[package]]
 name = "today"
 version = "0.1.0"
+dependencies = [
+ "chrono",
+]
+
+[[package]]
+name = "wasi"
+version = "0.10.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a143597ca7c7793eff794def352d41792a93c481eb1042423ff7ff72ba2c31f"
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/Cargo.toml b/Cargo.toml
index 69a316f..14aa956 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2018"
 
 [dependencies]
+chrono = "0.4.19"
diff --git a/README.md b/README.md
index 55be093..89680a9 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ DATE 2021-12-07 16:00
     Including empty lines (not even whitespace) in-between
     As long as the text stays indented, it's still part of it
 
-BIRTHDAY John Doe (<age>)
+BIRTHDAY John Doe
 DATE 1987-05-12
 
 BIRTHDAY Jane Doe
diff --git a/src/commands.rs b/src/commands.rs
new file mode 100644
index 0000000..e523e66
--- /dev/null
+++ b/src/commands.rs
@@ -0,0 +1,87 @@
+use chrono::{NaiveDate, NaiveDateTime, NaiveTime};
+
+#[derive(Debug)]
+struct DateDelta {
+    years: i32,
+    months: i32,
+    weeks: i32,
+    days: i32,
+}
+
+#[derive(Debug)]
+struct TimeDelta {
+    hours: i32,
+    minutes: i32,
+}
+
+#[derive(Debug)]
+enum EndDate {
+    Fixed(NaiveDate),
+    Delta(DateDelta),
+}
+
+#[derive(Debug)]
+enum EndTime {
+    Fixed(NaiveTime),
+    Delta(TimeDelta),
+}
+
+#[derive(Debug)]
+struct DateSpec {
+    start: NaiveDate,
+    end: Option<EndDate>,
+    repeat: Option<DateDelta>,
+}
+
+#[derive(Debug)]
+struct TimeSpec {
+    start: NaiveTime,
+    end: Option<EndTime>,
+}
+
+#[derive(Debug)]
+struct WhenSpec {
+    date: DateSpec,
+    time: Option<TimeSpec>,
+}
+
+#[derive(Debug)]
+struct Done {
+    refering_to: Option<NaiveDate>,
+    created_at: Option<NaiveDateTime>,
+}
+
+#[derive(Debug)]
+struct Task {
+    title: String,
+    when: Option<WhenSpec>,
+    desc: Option<String>,
+    dones: Vec<Done>,
+}
+
+#[derive(Debug)]
+struct Note {
+    title: String,
+    when: WhenSpec,
+    desc: Option<String>,
+}
+
+#[derive(Debug)]
+enum BirthdaySpec {
+    Date(NaiveDate),
+    DateWithoutYear { month: u8, day: u8 },
+}
+
+#[derive(Debug)]
+struct Birthday {
+    title: String,
+    when: BirthdaySpec,
+    desc: Option<String>,
+}
+
+#[derive(Debug)]
+enum Command {
+    Task(Task),
+    Note(Note),
+    Birthday(Birthday),
+}
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..b97e52d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+mod commands;
+
 fn main() {
     println!("Hello, world!");
 }