diff --git a/95_Weekday/javascript/weekday.js b/95_Weekday/javascript/weekday.js
index 276e1817..6070c71c 100644
--- a/95_Weekday/javascript/weekday.js
+++ b/95_Weekday/javascript/weekday.js
@@ -3,83 +3,345 @@
 // Converted from BASIC to Javascript by Oscar Toledo G. (nanochess)
 //
 
-function print(str)
-{
+/**
+ * Print given string to the end of the "output" element.
+ * @param str
+ */
+function print(str) {
     document.getElementById("output").appendChild(document.createTextNode(str));
 }
 
-function input()
-{
-    var input_element;
-    var input_str;
-    
+/**
+ * Obtain user input
+ * @returns {Promise<String>}
+ */
+function input() {
     return new Promise(function (resolve) {
-                       input_element = document.createElement("INPUT");
-                       
-                       print("? ");
-                       input_element.setAttribute("type", "text");
-                       input_element.setAttribute("length", "50");
-                       document.getElementById("output").appendChild(input_element);
-                       input_element.focus();
-                       input_str = undefined;
-                       input_element.addEventListener("keydown", function (event) {
-                                                      if (event.keyCode == 13) {
-                                                      input_str = input_element.value;
-                                                      document.getElementById("output").removeChild(input_element);
-                                                      print(input_str);
-                                                      print("\n");
-                                                      resolve(input_str);
-                                                      }
-                                                      });
-                       });
+        const input_element = document.createElement("INPUT");
+
+        print("? ");
+        input_element.setAttribute("type", "text");
+        input_element.setAttribute("length", "50");
+        document.getElementById("output").appendChild(input_element);
+        input_element.focus();
+        input_element.addEventListener("keydown", function (event) {
+            if (event.keyCode === 13) {
+                const input_str = input_element.value;
+                document.getElementById("output").removeChild(input_element);
+                print(input_str);
+                print("\n");
+                resolve(input_str);
+            }
+        });
+    });
 }
 
-function tab(space)
-{
-    var str = "";
-    while (space-- > 0)
+/**
+ * Create a string consisting of the given number of spaces
+ * @param spaceCount
+ * @returns {string}
+ */
+function tab(spaceCount) {
+    let str = "";
+    while (spaceCount-- > 0)
         str += " ";
     return str;
 }
 
-function fna(arg) {
-    return Math.floor(arg / 4);
+const MONTHS_PER_YEAR = 12;
+const DAYS_PER_COMMON_YEAR = 365;
+const DAYS_PER_IDEALISED_MONTH = 30;
+const MAXIMUM_DAYS_PER_MONTH = 31;
+// In a common (non-leap) year the day of the week for the first of each month moves by the following amounts.
+const COMMON_YEAR_MONTH_OFFSET = [0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5];
+
+/**
+ * Date representation.
+ */
+class DateStruct {
+    #year;
+    #month;
+    #day;
+
+    /**
+     * Build a DateStruct
+     * @param {number} year
+     * @param {number} month
+     * @param {number} day
+     */
+    constructor(year, month, day) {
+        this.#year = year;
+        this.#month = month;
+        this.#day = day;
+    }
+
+    get year() {
+        return this.#year;
+    }
+
+    get month() {
+        return this.#month;
+    }
+
+    get day() {
+        return this.#day;
+    }
+
+    /**
+     * Determine if the date could be a Gregorian date.
+     * Be aware the Gregorian calendar was not introduced in all places at once,
+     * see https://en.wikipedia.org/wiki/Gregorian_calendar
+     * @returns {boolean} true if date could be Gregorian; otherwise false.
+     */
+    isGregorianDate() {
+        let result = false;
+        if (this.#year > 1582) {
+            result = true;
+        } else if (this.#year === 1582) {
+            if (this.#month > 10) {
+                result = true;
+            } else if (this.#month === 10 && this.#day >= 15) {
+                result = true;
+            }
+        }
+        return result;
+    }
+
+    /**
+     * The following performs a hash on the day parts which guarantees that
+     * 1. different days will return different numbers
+     * 2. the numbers returned are ordered.
+     * @returns {number}
+     */
+    getNormalisedDay() {
+        return (this.year * MONTHS_PER_YEAR + this.month) * MAXIMUM_DAYS_PER_MONTH + this.day;
+    }
+
+    /**
+     * Determine the day of the week.
+     * This calculation returns a number between 1 and 7 where Sunday=1, Monday=2, ..., Saturday=7.
+     * @returns {number} Value between 1 and 7 representing Sunday to Saturday.
+     */
+    getDayOfWeek() {
+        // Calculate an offset based on the century part of the year.
+        const centuriesSince1500 = Math.floor((this.year - 1500) / 100);
+        let centuryOffset = centuriesSince1500 * 5 + (centuriesSince1500 + 3) / 4;
+        centuryOffset = Math.floor(centuryOffset % 7);
+
+        // Calculate an offset based on the shortened two digit year.
+        // January 1st moves forward by approximately 1.25 days per year
+        const yearInCentury = this.year % 100;
+        const yearInCenturyOffsets = yearInCentury / 4 + yearInCentury;
+
+        // combine offsets with day and month
+        let dayOfWeek = centuryOffset + yearInCenturyOffsets + this.day + COMMON_YEAR_MONTH_OFFSET[this.month - 1];
+
+        dayOfWeek = Math.floor(dayOfWeek % 7) + 1;
+        if (this.month <= 2 && this.isLeapYear()) {
+            dayOfWeek--;
+        }
+        if (dayOfWeek === 0) {
+            dayOfWeek = 7;
+        }
+        return dayOfWeek;
+    }
+
+    /**
+     * Determine if the given year is a leap year.
+     * @returns {boolean}
+     */
+    isLeapYear() {
+        if ((this.year % 4) !== 0) {
+            return false;
+        } else if ((this.year % 100) !== 0) {
+            return true;
+        } else if ((this.year % 400) !== 0) {
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Returns a US formatted date, i.e. Month/Day/Year.
+     * @returns {string}
+     */
+    toString() {
+        return this.#month + "/" + this.#day + "/" + this.#year;
+    }
 }
 
-function fnb(arg) {
-    return Math.floor(arg / 7);
-}
+/**
+ * Duration representation.
+ * Note: this class only handles positive durations well
+ */
+class Duration {
+    #years;
+    #months;
+    #days;
 
-var t = [, 0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5];
-
-var k5;
-var k6;
-var k7;
-
-function time_spent(f, a8)
-{
-    k1 = Math.floor(f * a8);
-    i5 = Math.floor(k1 / 365);
-    k1 -= i5 * 365;
-    i6 = Math.floor(k1 / 30);
-    i7 = k1 - (i6 * 30);
-    k5 -= i5;
-    k6 -= i6;
-    k7 -= i7;
-    if (k7 < 0) {
-        k7 += 30;
-        k6--;
+    /**
+     * Build a Duration
+     * @param {number} years
+     * @param {number} months
+     * @param {number} days
+     */
+    constructor(years, months, days) {
+        this.#years = years;
+        this.#months = months;
+        this.#days = days;
+        this.#fixRanges();
     }
-    if (k6 <= 0) {
-        k6 += 12;
-        k5--;
+
+    get years() {
+        return this.#years;
+    }
+
+    get months() {
+        return this.#months;
+    }
+
+    get days() {
+        return this.#days;
+    }
+
+    clone() {
+        return new Duration(this.#years, this.#months, this.#days);
+    }
+
+    /**
+     * Adjust Duration by removing years, months and days from supplied Duration.
+     * This is a naive calculation which assumes all months are 30 days.
+     * @param {Duration} timeToRemove
+     */
+    remove(timeToRemove) {
+        this.#years -= timeToRemove.years;
+        this.#months -= timeToRemove.months;
+        this.#days -= timeToRemove.days;
+        this.#fixRanges();
+    }
+
+    /**
+     * Move days and months into expected range.
+     */
+    #fixRanges() {
+        if (this.#days < 0) {
+            this.#days += DAYS_PER_IDEALISED_MONTH;
+            this.#months--;
+        }
+        if (this.#months < 0) {
+            this.#months += MONTHS_PER_YEAR;
+            this.#years--;
+        }
+    }
+
+    /**
+     * Computes an approximation of the days covered by the duration.
+     * The calculation assumes all years are 365 days, months are 30 days each,
+     * and adds on an extra bit the more months that have passed.
+     * @returns {number}
+     */
+    getApproximateDays() {
+        return (
+            (this.#years * DAYS_PER_COMMON_YEAR)
+            + (this.#months * DAYS_PER_IDEALISED_MONTH)
+            + this.#days
+            + Math.floor(this.#months / 2)
+        );
+    }
+
+    /**
+     * Returns a formatted duration with tab separated values, i.e. Years\tMonths\tDays.
+     * @returns {string}
+     */
+    toString() {
+        return this.#years + "\t" + this.#months + "\t" + this.#days;
+    }
+
+    /**
+     * Determine approximate Duration between two dates.
+     * This is a naive calculation which assumes all months are 30 days.
+     * @param {DateStruct} date1
+     * @param {DateStruct} date2
+     * @returns {Duration}
+     */
+    static between(date1, date2) {
+        let years = date1.year - date2.year;
+        let months = date1.month - date2.month;
+        let days = date1.day - date2.day;
+        return new Duration(years, months, days);
+    }
+
+    /**
+     * Calculate years, months and days as factor of days.
+     * This is a naive calculation which assumes all months are 30 days.
+     * @param dayCount Total day to convert to a duration
+     * @param factor   Factor to apply when calculating the duration
+     * @returns {Duration}
+     */
+    static fromDays(dayCount, factor) {
+        let totalDays = Math.floor(factor * dayCount);
+        const years = Math.floor(totalDays / DAYS_PER_COMMON_YEAR);
+        totalDays -= years * DAYS_PER_COMMON_YEAR;
+        const months = Math.floor(totalDays / DAYS_PER_IDEALISED_MONTH);
+        const days = totalDays - (months * DAYS_PER_IDEALISED_MONTH);
+        return new Duration(years, months, days);
     }
-    print(i5 + "\t" + i6 + "\t" + i7 + "\n");
 }
 
 // Main control section
-async function main()
-{
+async function main() {
+    /**
+     * Reads a date, and extracts the date information.
+     * This expects date parts to be comma separated, using US date ordering,
+     * i.e. Month,Day,Year.
+     * @returns {Promise<DateStruct>}
+     */
+    async function inputDate() {
+        let dateString = await input();
+        const month = parseInt(dateString);
+        const day = parseInt(dateString.substr(dateString.indexOf(",") + 1));
+        const year = parseInt(dateString.substr(dateString.lastIndexOf(",") + 1));
+        return new DateStruct(year, month, day);
+    }
+
+    /**
+     * Obtain text for the day of the week.
+     * @param {DateStruct} date
+     * @returns {string}
+     */
+    function getDayOfWeekText(date) {
+        const dayOfWeek = date.getDayOfWeek();
+        let dayOfWeekText = "";
+        switch (dayOfWeek) {
+            case 1:
+                dayOfWeekText = "SUNDAY.";
+                break;
+            case 2:
+                dayOfWeekText = "MONDAY.";
+                break;
+            case 3:
+                dayOfWeekText = "TUESDAY.";
+                break;
+            case 4:
+                dayOfWeekText = "WEDNESDAY.";
+                break;
+            case 5:
+                dayOfWeekText = "THURSDAY.";
+                break;
+            case 6:
+                if (date.day === 13) {
+                    dayOfWeekText = "FRIDAY THE THIRTEENTH---BEWARE!";
+                } else {
+                    dayOfWeekText = "FRIDAY.";
+                }
+                break;
+            case 7:
+                dayOfWeekText = "SATURDAY.";
+                break;
+        }
+        return dayOfWeekText;
+    }
+
     print(tab(32) + "WEEKDAY\n");
     print(tab(15) + "CREATIVE COMPUTING  MORRISTOWN, NEW JERSEY\n");
     print("\n");
@@ -89,111 +351,69 @@ async function main()
     print("GIVES FACTS ABOUT A DATE OF INTEREST TO YOU.\n");
     print("\n");
     print("ENTER TODAY'S DATE IN THE FORM: 3,24,1979  ");
-    str = await input();
-    m1 = parseInt(str);
-    d1 = parseInt(str.substr(str.indexOf(",") + 1));
-    y1 = parseInt(str.substr(str.lastIndexOf(",") + 1));
+    const today = await inputDate();
     // This program determines the day of the week
     //  for a date after 1582
     print("ENTER DAY OF BIRTH (OR OTHER DAY OF INTEREST)");
-    str = await input();
-    m = parseInt(str);
-    d = parseInt(str.substr(str.indexOf(",") + 1));
-    y = parseInt(str.substr(str.lastIndexOf(",") + 1));
+    const dateOfBirth = await inputDate();
     print("\n");
-    i1 = Math.floor((y - 1500) / 100);
     // Test for date before current calendar.
-    if (y - 1582 < 0) {
-        print("NOT PREPARED TO GIVE DAY OF WEEK PRIOR TO MDLXXXII.\n");
+    if (!dateOfBirth.isGregorianDate()) {
+        print("NOT PREPARED TO GIVE DAY OF WEEK PRIOR TO X.XV.MDLXXXII.\n");
     } else {
-        a = i1 * 5 + (i1 + 3) / 4;
-        i2 = Math.floor(a - fnb(a) * 7);
-        y2 = Math.floor(y / 100);
-        y3 = Math.floor(y - y2 * 100);
-        a = y3 / 4 + y3 + d + t[m] + i2;
-        b = Math.floor(a - fnb(a) * 7) + 1;
-        if (m <= 2) {
-            if (y3 != 0) {
-                t1 = Math.floor(y - fna(y) * 4);
-            } else {
-                a = i1 - 1;
-                t1 = Math.floor(a - fna(a) * 4);
-            }
-            if (t1 == 0) {
-                if (b == 0)
-                    b = 6;
-                b--;
-            }
-        }
-        if (b == 0)
-            b = 7;
-        if ((y1 * 12 + m1) * 31 + d1 < (y * 12 + m) * 31 + d) {
-            print(m + "/" + d + "/" + y + " WILL BE A ");
-        } else if ((y1 * 12 + m1) * 31 + d1 == (y * 12 + m) * 31 + d) {
-            print(m + "/" + d + "/" + y + " IS A ");
+        const normalisedToday = today.getNormalisedDay();
+        const normalisedDob = dateOfBirth.getNormalisedDay();
+
+        let dayOfWeekText = getDayOfWeekText(dateOfBirth);
+        if (normalisedToday < normalisedDob) {
+            print(dateOfBirth + " WILL BE A " + dayOfWeekText + "\n");
+        } else if (normalisedToday === normalisedDob) {
+            print(dateOfBirth + " IS A " + dayOfWeekText + "\n");
         } else {
-            print(m + "/" + d + "/" + y + " WAS A ");
+            print(dateOfBirth + " WAS A " + dayOfWeekText + "\n");
         }
-        switch (b) {
-            case 1: print("SUNDAY.\n"); break;
-            case 2: print("MONDAY.\n"); break;
-            case 3: print("TUESDAY.\n"); break;
-            case 4: print("WEDNESDAY.\n"); break;
-            case 5: print("THURSDAY.\n"); break;
-            case 6:
-                if (d == 13) {
-                    print("FRIDAY THE THIRTEENTH---BEWARE!\n");
-                } else {
-                    print("FRIDAY.\n");
-                }
-                break;
-            case 7: print("SATURDAY.\n"); break;
-        }
-        if ((y1 * 12 + m1) * 31 + d1 != (y * 12 + m) * 31 + d) {
-            i5 = y1 - y;
+
+        if (normalisedToday !== normalisedDob) {
             print("\n");
-            i6 = m1 - m;
-            i7 = d1 - d;
-            if (i7 < 0) {
-                i6--;
-                i7 += 30;
-            }
-            if (i6 < 0) {
-                i5--;
-                i6 += 12;
-            }
-            if (i5 >= 0) {
-                if (i7 == 0 && i6 == 0)
+            let differenceBetweenDates = Duration.between(today, dateOfBirth);
+            if (differenceBetweenDates.years >= 0) {
+                if (differenceBetweenDates.days === 0 && differenceBetweenDates.months === 0) {
                     print("***HAPPY BIRTHDAY***\n");
+                }
                 print("                        \tYEARS\tMONTHS\tDAYS\n");
                 print("                        \t-----\t------\t----\n");
-                print("YOUR AGE (IF BIRTHDATE) \t" + i5 + "\t" + i6 + "\t" + i7 + "\n");
-                a8 = (i5 * 365) + (i6 * 30) + i7 + Math.floor(i6 / 2);
-                k5 = i5;
-                k6 = i6;
-                k7 = i7;
-                // Calculate retirement date.
-                e = y + 65;
-                // Calculate time spent in the following functions.
-                print("YOU HAVE SLEPT \t\t\t");
-                time_spent(0.35, a8);
-                print("YOU HAVE EATEN \t\t\t");
-                time_spent(0.17, a8);
-                if (k5 <= 3) {
-                    print("YOU HAVE PLAYED \t\t\t");
-                } else if (k5 <= 9) {
-                    print("YOU HAVE PLAYED/STUDIED \t\t");
+                print("YOUR AGE (IF BIRTHDATE) \t" + differenceBetweenDates + "\n");
+
+                const approximateDaysBetween = differenceBetweenDates.getApproximateDays();
+                const unaccountedTime = differenceBetweenDates.clone();
+
+                // 35% sleeping
+                const sleepTimeSpent = Duration.fromDays(approximateDaysBetween, 0.35);
+                print("YOU HAVE SLEPT \t\t\t" + sleepTimeSpent + "\n");
+                unaccountedTime.remove(sleepTimeSpent);
+
+                // 17% eating
+                const eatenTimeSpent = Duration.fromDays(approximateDaysBetween, 0.17);
+                print("YOU HAVE EATEN \t\t\t" + eatenTimeSpent + "\n");
+                unaccountedTime.remove(eatenTimeSpent);
+
+                // 23% working, studying or playing
+                const workPlayTimeSpent = Duration.fromDays(approximateDaysBetween, 0.23);
+                if (unaccountedTime.years <= 3) {
+                    print("YOU HAVE PLAYED \t\t" + workPlayTimeSpent + "\n");
+                } else if (unaccountedTime.years <= 9) {
+                    print("YOU HAVE PLAYED/STUDIED \t" + workPlayTimeSpent + "\n");
                 } else {
-                    print("YOU HAVE WORKED/PLAYED \t\t");
+                    print("YOU HAVE WORKED/PLAYED \t\t" + workPlayTimeSpent + "\n");
                 }
-                time_spent(0.23, a8);
-                if (k6 == 12) {
-                    k5++;
-                    k6 = 0;
-                }
-                print("YOU HAVE RELAXED \t\t" + k5 + "\t" + k6 + "\t" + k7 + "\n");
+                unaccountedTime.remove(workPlayTimeSpent);
+
+                // Remaining time spent relaxing
+                print("YOU HAVE RELAXED \t\t" + unaccountedTime + "\n");
+
+                const retirementYear = dateOfBirth.year + 65;
                 print("\n");
-                print(tab(16) + "***  YOU MAY RETIRE IN " + e + " ***\n");
+                print(tab(16) + "***  YOU MAY RETIRE IN " + retirementYear + " ***\n");
                 print("\n");
             }
         }