diff --git a/server/api/auth.js b/server/api/auth.js
index 6e0ea35..c33308e 100644
--- a/server/api/auth.js
+++ b/server/api/auth.js
@@ -3,64 +3,69 @@ const prisma = new Prisma.PrismaClient();
 
 import { log } from "../logs.js";
 
-export class Auth {
-  constructor() {}
-  login = async (req, res) => {
-    if (!req.body.password) {
-      res.redirect("/login");
-      return;
-    } else {
-      if (req.body.password == process.env.AUTH_PASSWORD) {
-        const session = await prisma.session.create({
-          data: {
-            validUntil: new Date(Date.now() + 1000 * 60 * 60 * 24 * 14), // Expires after 14 days
-          },
-        });
-        res.cookie("session", session.token, {
-          httpOnly: true,
-          expires: new Date(253402300000000),
-        });
-        log("API / Auth", `New session: ${session.token}`);
-        res.redirect("/");
-      } else {
-        res.redirect("/login");
-        return;
-      }
-    }
-  };
-  checkLogin = async (req, res, next) => {
-    if (!process.env.AUTH_PASSWORD) {
-      next();
-      return;
-    }
-    if (!req.cookies.session) {
-      res.sendStatus(401);
-      return;
-    } else {
-      const session = await prisma.session.findUnique({
-        where: {
-          token: req.cookies.session,
-        },
-      });
-      if (!session) {
-        res.sendStatus(401);
-        return;
-      }
-      // Renew session expiration date
-      await prisma.session.update({
-        where: {
-          token: session.token,
-        },
-        data: {
-          validUntil: new Date(Date.now() + 1000 * 60 * 60 * 24 * 14),
-        },
-      });
-    }
-    next();
-  };
+async function login(req, res) {
+  // Check password
+  if (!req.body.password || req.body.password != process.env.AUTH_PASSWORD) {
+    res.redirect("/login");
+    return;
+  }
+  // Create a new auth session
+  const session = await prisma.session.create({
+    data: {
+      // Expires after 14 days of inactivity
+      validUntil: new Date(Date.now() + 1000 * 60 * 60 * 24 * 14),
+    },
+  });
+  res.cookie("session", session.token, {
+    httpOnly: true,
+    // Expire "never"
+    expires: new Date(253402300000000),
+  });
+  log("API / Auth", `New session: ${session.token}`);
+  res.redirect("/");
 }
 
-// Check for expired sessions every hour
+async function checkLogin(req, res, next) {
+  // If AUTH_PASSWORD env variable is not present don't require any login
+  if (!process.env.AUTH_PASSWORD) {
+    next();
+    return;
+  }
+  // If no session cookie is set send 401 Unauthorized
+  // so the app redirects to the login page
+  if (!req.cookies.session) {
+    res.sendStatus(401);
+    return;
+  }
+  // Check the provided session cookie
+  const session = await prisma.session.findUnique({
+    where: {
+      token: req.cookies.session,
+    },
+  });
+  // If no session is found also send 401
+  if (!session) {
+    res.sendStatus(401);
+    return;
+  }
+  // Renew session expiration date
+  await prisma.session.update({
+    where: {
+      token: session.token,
+    },
+    data: {
+      validUntil: new Date(Date.now() + 1000 * 60 * 60 * 24 * 14),
+    },
+  });
+  next();
+}
+
+export default {
+  login,
+  checkLogin,
+};
+
+// Clean up expired sessions every hour
 setInterval(async () => {
   const sessions = await prisma.session.findMany();
   for (const session of sessions) {
diff --git a/server/api/index.js b/server/api/index.js
index 9fe13f7..1d85213 100644
--- a/server/api/index.js
+++ b/server/api/index.js
@@ -22,7 +22,7 @@ export async function getTimetable(req, res) {
     },
   });
   if (!timetable) {
-    res.status(400).send({
+    res.status(404).send({
       success: false,
       error: "no_timetable",
       message: "No timetable was found for this class",
@@ -44,7 +44,7 @@ function convertToDate(dateQuery) {
   if (dateQuery.match(/^[0-9]+$/) != null) date = parseInt(dateQuery);
   else date = dateQuery;
   date = new Date(date).setUTCHours(0, 0, 0, 0);
-  return date;
+  return new Date(date);
 }
 
 // Get substitutions API endpoint (/api/substitutions)
@@ -75,11 +75,11 @@ export async function getSubstitutions(req, res) {
   // Choose which date to use in database query
   if (from && to) {
     prismaOptions.where.date = {
-      gte: new Date(from),
-      lte: new Date(to),
+      gte: from,
+      lte: to,
     };
   } else if (date) {
-    prismaOptions.where.date = new Date(date);
+    prismaOptions.where.date = date;
   } else {
     // Default to all substitutions for today and in the future
     prismaOptions.where.date = {
@@ -140,11 +140,11 @@ export async function getHistory(req, res) {
   // Choose which date to use in database query
   if (from && to) {
     prismaOptions.where.substitution.date = {
-      gte: new Date(from),
-      lte: new Date(to),
+      gte: from,
+      lte: to,
     };
   } else if (date) {
-    prismaOptions.where.substitution.date = new Date(date);
+    prismaOptions.where.substitution.date = date;
   } else {
     // Default to history of all substitutions for today and in the future
     prismaOptions.where.substitution.date = {
@@ -173,7 +173,7 @@ export async function getHistory(req, res) {
 // Get classes API endpoints (/api/classes)
 // Get all available classes where timetable and
 // substitutions can be requested for
-export async function getClasses(req, res) {
+export async function getClasses(_req, res) {
   const classes = await prisma.class.findMany({
     select: {
       name: true,
diff --git a/server/index.js b/server/index.js
index 6f54d8a..1146741 100644
--- a/server/index.js
+++ b/server/index.js
@@ -9,7 +9,7 @@ import {
   getHistory,
   getClasses,
 } from "./api/index.js";
-import { Auth } from "./api/auth.js";
+import auth from "./api/auth.js";
 import { Parser } from "./parser/index.js";
 
 // Check DSB Mobile credentials are supplied
@@ -34,7 +34,6 @@ new Parser(
 );
 
 // Create new Auth class to store sessions
-const auth = new Auth();
 app.post("/login", auth.login);
 // Check login for every API request
 app.use("/api", auth.checkLogin);
diff --git a/server/parser/dsbmobile.js b/server/parser/dsbmobile.js
index e428adb..8a01354 100644
--- a/server/parser/dsbmobile.js
+++ b/server/parser/dsbmobile.js
@@ -5,7 +5,7 @@ export async function getAuthtoken(username, password) {
   const response = await axios.get(
     `${baseUrl}/authid?user=${username}&password=${password}&bundleid&appversion&osversion&pushid`
   );
-  if (response.data == "") throw "Wrong username or password";
+  if (response.data == "") throw "Wrong DSB username or password";
   return response.data;
 }
 
diff --git a/server/parser/index.js b/server/parser/index.js
index 4de7c4e..1d37f32 100644
--- a/server/parser/index.js
+++ b/server/parser/index.js
@@ -28,9 +28,9 @@ export class Parser {
       const plans = [];
       for (const entry of data) {
         // Download the substitution plan
-        const data = await this.fetchFile(entry.url);
+        const file = await this.fetchFile(entry.url);
         // Parse the substitution plan
-        const parsed = parseSubstitutionPlan(data);
+        const parsed = parseSubstitutionPlan(file);
         plans.push(parsed);
       }
       // Create a new parse event