diff --git a/src/app/app.rs b/src/app/app.rs
index 2fab85e..6a9e8b2 100644
--- a/src/app/app.rs
+++ b/src/app/app.rs
@@ -1,8 +1,5 @@
 use std::{
-    cmp::{max, min},
-    collections::HashMap,
-    io,
-    path::PathBuf,
+    cmp::{max, min}, collections::HashMap, fs, io, path::PathBuf, time::SystemTime
 };
 
 use ratatui::{
@@ -27,6 +24,7 @@ pub struct App {
     pub grid: Grid,
     pub mode: Mode,
     pub file: Option<PathBuf>,
+    file_modified_date: SystemTime,
     pub msg: StatusMessage,
     pub vars: HashMap<String, String>,
     pub screen: ScreenSpace,
@@ -211,13 +209,24 @@ impl App {
             screen: ScreenSpace::new(),
             marks: HashMap::new(),
             clipboard: Clipboard::new(),
+            file_modified_date: SystemTime::now(),
         }
     }
 
     pub fn new_with_file(file: impl Into<PathBuf> + Clone) -> std::io::Result<Self> {
         let mut app = Self::new();
         app.file = Some(file.clone().into());
-        app.grid = Grid::new_from_file(file.into())?;
+
+        let mut file = fs::OpenOptions::new().read(true).open(file.into())?;
+        let metadata = file.metadata()?;
+        // Not all systems support this, apparently.
+        if let Ok(time) = metadata.modified() {
+            app.file_modified_date = time;
+        } else {
+            // Default is to just assume it was modified when we opened it.
+        }
+
+        app.grid = Grid::new_from_file(&mut file)?;
         Ok(app)
     }
 
diff --git a/src/app/logic/calc.rs b/src/app/logic/calc.rs
index b422ef5..1dee174 100644
--- a/src/app/logic/calc.rs
+++ b/src/app/logic/calc.rs
@@ -1,8 +1,8 @@
 use std::{
     cmp::{max, min},
-    fs,
+    fs::{self, File},
     io::{Read, Write},
-    path::PathBuf,
+    path::PathBuf
 };
 
 use evalexpr::*;
@@ -58,10 +58,9 @@ impl Grid {
         }
     }
 
-    pub fn new_from_file(path: impl Into<PathBuf>) -> std::io::Result<Self> {
+    pub fn new_from_file(file: &mut File) -> std::io::Result<Self> {
         let mut grid = Self::new();
 
-        let mut file = fs::OpenOptions::new().read(true).open(path.into())?;
         let mut buf = String::new();
         file.read_to_string(&mut buf)?;
         for (yi, line) in buf.lines().enumerate() {
diff --git a/src/app/mode.rs b/src/app/mode.rs
index e664633..a516003 100644
--- a/src/app/mode.rs
+++ b/src/app/mode.rs
@@ -1,7 +1,5 @@
 use std::{
-    cmp::{max, min},
-    fmt::Display,
-    path::PathBuf,
+    cmp::{max, min}, fmt::Display, fs, path::PathBuf
 };
 
 use ratatui::{
@@ -83,6 +81,9 @@ impl Mode {
                             }
                         };
 
+                        // TODO Check if the file exists, but the program wasn't opened with it. We might be accidentally overwriting something else.
+                        // let mut file = fs::OpenOptions::new().write(true).append(false).truncate(true).create(true).open(path)?;
+
                         if let Err(e) = app.grid.save_to(&path) {
                             app.msg = StatusMessage::error(format!("{e}"));
                         } else {