Use Luxon to manipulate dates

package.json

@@ -15,7 +15,11 @@
         "dev:server": "grunt dev:server",
         "deploy": "grunt deploy"
     },
+    "dependencies": {
+        "luxon": "^2.3.1"
+    },
     "devDependencies": {
+        "@types/luxon": "^2.3.0",
         "grunt": "^1.4.1",
         "grunt-cli": "^1.4.3",
         "grunt-contrib-clean": "^2.0.0",

src/main/js/Main.ts

@@ -1,6 +1,8 @@
 // @ts-ignore
 const {$, doAfterLoad, footer, header, nav} = window.fwdekker;
 
+import {DateTime} from "luxon";
+
 
 /**
  * Returns a number between `min` (inclusive) and `max` (inclusive).
@@ -255,7 +257,7 @@ class DoomsdayDate {
     /**
      * The underlying date.
      */
-    readonly date: Date;
+    readonly date: DateTime;
 
 
     /**
@@ -263,7 +265,7 @@ class DoomsdayDate {
      *
      * @param date the date to be wrapped
      */
-    constructor(date: Date) {
+    constructor(date: DateTime) {
         this.date = date;
     }
 
@@ -274,7 +276,7 @@ class DoomsdayDate {
      * @return the number of this `DoomsdayDate`'s century
      */
     getCentury(): number {
-        return Math.floor(this.date.getFullYear() / 100);
+        return Math.floor(this.date.year / 100);
     }
 
     /**
@@ -283,8 +285,7 @@ class DoomsdayDate {
      * @return the day of the week of the anchor of this `DoomsdayDate`'s century
      */
     getCenturyAnchorString(): string {
-        const centuryAnchorNumber = (5 * (this.getCentury() % 4)) % 7 + 2;
-        return DoomsdayDate.getWeekDayOf(centuryAnchorNumber);
+        return this.date.set({year: this.getCentury() * 100, month: 4, day: 4}).setLocale("en-US").weekdayLong;
     };
 
     /**
@@ -293,11 +294,7 @@ class DoomsdayDate {
      * @return the day of the week of the anchor day of this `DoomsdayDate`'s year
      */
     getYearAnchorString(): string {
-        const anchorDate = new Date(this.date);
-        anchorDate.setDate(4); // 4th
-        anchorDate.setMonth(3); // April
-        anchorDate.setHours(0); // midnight local time
-        return DoomsdayDate.getWeekDayOf(anchorDate);
+        return this.date.set({day: 4, month: 4}).setLocale("en-US").weekdayLong;
     };
 
     /**
@@ -306,41 +303,10 @@ class DoomsdayDate {
      * @return the day of the week of this `DoomsdayDate`
      */
     getWeekdayString(): string {
-        return DoomsdayDate.getWeekDayOf(this.date);
+        return this.date.setLocale("en-US").weekdayLong;
     };
 
 
-    /**
-     * Returns the week day of [date].
-     *
-     * @param date the date to get the week day of; if it is a `number`, then 0 corresponds to Sunday
-     * @return the name of the week day corresponding to [date]
-     */
-    static getWeekDayOf(date: Date|number): string {
-        if (date instanceof Date) {
-            return date.toLocaleString("en-US", {weekday: "long"});
-        } else {
-            switch (date % 7) {
-                case 0:
-                    return "Sunday";
-                case 1:
-                    return "Monday";
-                case 2:
-                    return "Tuesday";
-                case 3:
-                    return "Wednesday";
-                case 4:
-                    return "Thursday";
-                case 5:
-                    return "Friday";
-                case 6:
-                    return "Saturday";
-                default:
-                    throw new Error(`Unexpected weekday number '${date}'.`);
-            }
-        }
-    };
-
     /**
      * Returns the day of the week corresponding to `dayString`, or an empty string if no day was recognized.
      *
@@ -377,9 +343,9 @@ class DoomsdayDate {
      */
     static random() {
         // TODO Give custom date range to this method
-        const minDate = new Date("0001-01-01").getTime() / 86400000;
-        const maxDate = new Date("9999-12-31").getTime() / 86400000;
-        return new DoomsdayDate(new Date(generateRandom(minDate, maxDate) * 86400000));
+        const startDate = DateTime.utc(1, 1, 1);
+        const dayRange = 9999 * 365 + (10000 / 400 * 97) - 1;
+        return new DoomsdayDate(startDate.plus({days: generateRandom(0, dayRange)}))
     }
 }
 
@@ -467,7 +433,7 @@ doAfterLoad(() => {
 
         updateTitle() {
             if (yearDetails.isOpened())
-                this.titleLabel.innerText = `Doomsday of year ${quizDate.date.getFullYear()}?`;
+                this.titleLabel.innerText = `Doomsday of year ${quizDate.date.year}?`;
             else
                 this.titleLabel.innerText = `Year`;
         }
@@ -491,7 +457,7 @@ doAfterLoad(() => {
         }
 
         updateTitle() {
-            this.titleLabel.innerText = `Weekday of ${quizDate.date.toISOString().substring(0, 10)}?`;
+            this.titleLabel.innerText = `Weekday of ${quizDate.date.toISODate()}?`;
         }
     }($("#day-input"), $("#day-title-label"), $("#day-submit"));
 
@@ -509,7 +475,7 @@ doAfterLoad(() => {
     function reloadQuiz() {
         quizDate = DoomsdayDate.random();
         console.log("# Reset");
-        console.log(`New date:  ${quizDate.date.toISOString().substring(0, 10)}`);
+        console.log(`New date:  ${quizDate.date.toISODate()}`);
         console.log(`           ${quizDate.date}`);
         console.log(`Century#:  ${quizDate.getCentury()}`);
         console.log(`Century:   ${quizDate.getCenturyAnchorString()}`);