diff --git a/.gitignore b/.gitignore
index ea8c4bf..df76ce4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /target
+*.pest
diff --git a/Cargo.lock b/Cargo.lock
index 1c90227..7e190d3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,15 +2,87 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "datetime"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44c3f7a77f3e57fedf80e09136f2d8777ebf621207306f6d96d610af048354bc"
+dependencies = [
+ "libc",
+ "locale",
+ "pad",
+ "redox_syscall",
+ "winapi",
+]
+
 [[package]]
 name = "grammatical"
 version = "0.1.0"
 dependencies = [
+ "datetime",
  "unicode-ident",
 ]
 
+[[package]]
+name = "libc"
+version = "0.2.153"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"
+
+[[package]]
+name = "locale"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fdbe492a9c0238da900a1165c42fc5067161ce292678a6fe80921f30fe307fd"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "pad"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2ad9b889f1b12e0b9ee24db044b5129150d5eada288edc800f789928dc8c0e3"
+dependencies = [
+ "unicode-width",
+]
+
+[[package]]
+name = "redox_syscall"
+version = "0.1.57"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41cc0f7e4d5d4544e8861606a285bb08d3e70712ccc7d2b84d7c0ccfaf4b05ce"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
+
+[[package]]
+name = "unicode-width"
+version = "0.1.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e51733f11c9c4f72aa0c160008246859e340b00807569a0da0e7a1079b27ba85"
+
+[[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 90a72de..09047fd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,5 +3,13 @@ name = "grammatical"
 version = "0.1.0"
 edition = "2021"
 
+[features]
+default = []
+datetime = ["dep:datetime"]
+conlang = []
+
 [dependencies]
+datetime = { version = "0.5.2", features = [
+    "format",
+], default_features = false, optional = true }
 unicode-ident = "1.0.12"
diff --git a/src/conlang.rs b/src/conlang.rs
new file mode 100644
index 0000000..be46b35
--- /dev/null
+++ b/src/conlang.rs
@@ -0,0 +1,7 @@
+#[cfg(feature = "conlang")]
+const CONLANG_SUPPLEMENTAL: &str = include_str!("conlang-supplemental.pest");
+
+pub fn print_supplemental() {
+    #[cfg(feature = "conlang")]
+    println!("\n// CONLANG_SUPPLEMENTAL\n{CONLANG_SUPPLEMENTAL}");
+}
diff --git a/src/datetime.rs b/src/datetime.rs
new file mode 100644
index 0000000..cd75c68
--- /dev/null
+++ b/src/datetime.rs
@@ -0,0 +1,16 @@
+#[cfg(feature = "datetime")]
+use datetime::{LocalDateTime, ISO};
+
+#[cfg(feature = "datetime")]
+struct Now(LocalDateTime);
+#[cfg(feature = "datetime")]
+impl std::fmt::Display for Now {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+pub fn print_current_time() {
+    #[cfg(feature = "datetime")]
+    println!("// Generated {}", Now(LocalDateTime::now()))
+}
diff --git a/src/main.rs b/src/main.rs
index 66bae46..841aa4b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,19 +1,25 @@
+use grammatical::*;
 use std::error::Error;
 
-use grammatical::*;
+mod conlang;
+mod datetime;
 
 fn main() -> Result<(), Box<dyn Error>> {
-    for file in std::env::args().skip(1) {
+    datetime::print_current_time();
+    let args: Vec<_> = std::env::args().skip(1).collect();
+    if args.is_empty() {
+        for line in std::io::stdin().lines() {
+            let line = line?;
+            let mut p = Parser::new(&line);
+            parse(&mut p);
+        }
+    }
+    for file in args {
         let file = std::fs::read_to_string(file)?;
         let mut p = Parser::new(&file);
         parse(&mut p);
     }
-
-    for line in std::io::stdin().lines() {
-        let line = line?;
-        let mut p = Parser::new(&line);
-        parse(&mut p);
-    }
+    conlang::print_supplemental();
     Ok(())
 }