diff --git a/src/files.rs b/src/files.rs
index 0fbb151..addce9d 100644
--- a/src/files.rs
+++ b/src/files.rs
@@ -11,9 +11,21 @@ pub mod commands;
 mod format;
 mod parse;
 
+#[derive(Debug)]
+struct LoadedFile {
+    file: File,
+    dirty: bool,
+}
+
+impl LoadedFile {
+    pub fn new(file: File) -> Self {
+        Self { file, dirty: false }
+    }
+}
+
 #[derive(Debug)]
 pub struct Files {
-    files: HashMap<PathBuf, File>,
+    files: HashMap<PathBuf, LoadedFile>,
     timezone: Tz,
 }
 
@@ -42,7 +54,7 @@ impl Files {
         Ok(Self { files, timezone })
     }
 
-    fn load_file(files: &mut HashMap<PathBuf, File>, path: &Path) -> Result<()> {
+    fn load_file(files: &mut HashMap<PathBuf, LoadedFile>, path: &Path) -> Result<()> {
         let canon_path = path.canonicalize()?;
         if files.contains_key(&canon_path) {
             // We've already loaded this exact file.
@@ -53,31 +65,34 @@ impl Files {
         let file = parse::parse(path, &content)?;
         let includes = file.includes.clone();
 
-        files.insert(canon_path, file);
+        files.insert(canon_path, LoadedFile::new(file));
 
         for include in includes {
-            Self::load_file(files, &include)?;
+            // Since we've successfully opened the file, its name can't be the
+            // root directory or empty string and must thus have a parent.
+            let include_path = path.parent().unwrap().join(include);
+            Self::load_file(files, &include_path)?;
         }
 
         Ok(())
     }
 
-    fn determine_timezone(files: &HashMap<PathBuf, File>) -> Result<Tz> {
+    fn determine_timezone(files: &HashMap<PathBuf, LoadedFile>) -> Result<Tz> {
         let mut found: Option<(PathBuf, String)> = None;
 
         for file in files.values() {
-            if let Some(file_tz) = &file.timezone {
+            if let Some(file_tz) = &file.file.timezone {
                 if let Some((found_name, found_tz)) = &found {
                     if found_tz != file_tz {
                         return Err(Error::TzConflict {
                             file1: found_name.clone(),
                             tz1: found_tz.clone(),
-                            file2: file.name.clone(),
+                            file2: file.file.name.clone(),
                             tz2: file_tz.clone(),
                         });
                     }
                 } else {
-                    found = Some((file.name.clone(), file_tz.clone()));
+                    found = Some((file.file.name.clone(), file_tz.clone()));
                 }
             }
         }
@@ -89,6 +104,26 @@ impl Files {
         })
     }
 
+    pub fn save(&self) -> Result<()> {
+        for (path, file) in &self.files {
+            if file.dirty {
+                Self::save_file(path, &file.file)?;
+            }
+        }
+        Ok(())
+    }
+
+    fn save_file(path: &Path, file: &File) -> Result<()> {
+        fs::write(path, &format!("{}", file))?;
+        Ok(())
+    }
+
+    pub fn mark_all_dirty(&mut self) {
+        for (_, file) in self.files.iter_mut() {
+            file.dirty = true;
+        }
+    }
+
     pub fn now(&self) -> DateTime<&Tz> {
         Utc::now().with_timezone(&&self.timezone)
     }
diff --git a/src/files/commands.rs b/src/files/commands.rs
index 58dbd92..1c4283a 100644
--- a/src/files/commands.rs
+++ b/src/files/commands.rs
@@ -329,7 +329,7 @@ pub enum Command {
 #[derive(Debug)]
 pub struct File {
     pub name: PathBuf,
-    pub includes: Vec<PathBuf>,
+    pub includes: Vec<String>,
     pub timezone: Option<String>,
     pub commands: Vec<Command>,
 }
diff --git a/src/files/format.rs b/src/files/format.rs
index 0e311e2..3cf5e01 100644
--- a/src/files/format.rs
+++ b/src/files/format.rs
@@ -273,14 +273,28 @@ impl fmt::Display for Command {
 
 impl fmt::Display for File {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let mut commands = self.commands.iter();
-        if let Some(command) = commands.next() {
-            write!(f, "{}", command)?;
-            for command in commands {
-                writeln!(f)?;
-                write!(f, "{}", command)?;
-            }
+        let mut empty = true;
+        for include in &self.includes {
+            writeln!(f, "INCLUDE {}", include)?;
+            empty = false;
         }
+
+        if let Some(tz) = &self.timezone {
+            if !empty {
+                writeln!(f)?;
+            }
+            writeln!(f, "TIMEZONE {}", tz)?;
+            empty = false;
+        }
+
+        for command in &self.commands {
+            if !empty {
+                writeln!(f)?;
+            }
+            write!(f, "{}", command)?;
+            empty = false;
+        }
+
         Ok(())
     }
 }
diff --git a/src/files/parse.rs b/src/files/parse.rs
index 129ceda..7e4433a 100644
--- a/src/files/parse.rs
+++ b/src/files/parse.rs
@@ -706,12 +706,7 @@ fn parse_command(p: Pair<Rule>, file: &mut File) -> Result<()> {
 
     let p = p.into_inner().next().unwrap();
     match p.as_rule() {
-        Rule::include => {
-            // Since we've successfully opened the file, its name can't be the
-            // root directory or empty string and must thus have a parent.
-            let parent = file.name.parent().unwrap();
-            file.includes.push(parent.join(parse_include(p)));
-        }
+        Rule::include => file.includes.push(parse_include(p)),
         Rule::timezone => match file.timezone {
             None => file.timezone = Some(parse_timezone(p)),
             Some(_) => fail(p.as_span(), "cannot set timezone multiple times")?,
diff --git a/src/main.rs b/src/main.rs
index 4db3574..19a33a4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,7 +15,12 @@ pub struct Opt {
 
 fn main() -> anyhow::Result<()> {
     let opt = Opt::from_args();
-    let files = Files::load(&opt.file)?;
+
+    let mut files = Files::load(&opt.file)?;
     println!("{}", files.now().format("%F %T %Z"));
+
+    files.mark_all_dirty();
+    files.save()?;
+
     Ok(())
 }