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‎config.json‎

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"template-strings"
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],
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"status": "beta"
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},
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{
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"slug": "appointment-time",
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"name": "Appointment Time",
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"uuid": "0f694053-a388-457f-89ca-f49be4560469",
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"concepts": [
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"dates"
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],
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"prerequisites": [
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"classes",
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"objects",
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"conditionals",
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"type-conversion"
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],
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"status": "beta"
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}
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],
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"practice": [

‎exercises/concept/appointment-time/.docs/hints.md‎

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# Hints
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## 1. Create an appointment
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- You need to create a new date. The introduction elaborates on the different ways.
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- `Date.now()` gives you current time in milliseconds
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- A day consist of 24 hour. An hour consist of 60 minutes. A minute consist of 60 seconds. A second consist of 1000 milliseconds. In order to get timestamp of `n` days later from current date, you can sum current timestamp and `n * 24 * 60 * 60 * 1000`.
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## 2. Convert a date into a timestamp
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- The introduction lists the various ways how to convert a date to different types. Can you use one of those methods?
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## 3. Get the details of an appointment
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- The introduction has all the required information to extract the information from a date.
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## 4. Update an appointment with the given options
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- The introduction has all the required information to extract the information from a date.
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- You can reuse `getAppointmentDetails`
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## 5. Get available times between two appointments
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- General subtraction between two dates will give you the timestamp between the two dates.
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- You probably want to convert to a number first, and not rely on type-coercion.
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## 6. Check if an appointment is now valid or not
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- Conditional operators will help you to decide which date is bigger or smaller between two dates.

‎exercises/concept/appointment-time/.docs/instructions.md‎

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# Instructions
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In this exercise you will work on some functions in order to manage appointments.
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The system stores everything in ISO 8601 formatted strings, but that's not how people use the calendar.
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Various functions are necessary to convert between the various formats.
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## 1. Create an appointment
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Create an appointment `n` days from now at current time.
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The function takes `n` days and return the appointment time of `n` days from now.
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```javascript
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createAppointment(4, now);
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// Given now is Sun Oct 05 2022 23:28:43 GMT+0600 (Bangladesh Standard Time)
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// => Sun Oct 09 2022 23:28:43 GMT+0600 (Bangladesh Standard Time)
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```
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If the second parameter `now` is unused, the current time should be used instead.
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## 2. Convert a date into a timestamp
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Various tools only work with the internationally standardized ISO 8601 format.
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Write the function `getAppointmentTimestamp` to take a date and return a string in that format.
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```javascript
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const appointment = new Date(Date.UTC(2010, 6, 16, 12, 42, 0, 0));
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getAppointmentTimestamp(appointment);
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// => '2010-07-16T12:42:00.000Z'
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```
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## 3. Get the details of an appointment
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Timestamps are hard to read; a function to get the appointment details should help with that.
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The function `getAppointmentDetails` takes a timestamp in the ISO 8601 format, and returns the year, month, date, hour, and minute.
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```javascript
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getAppointmentDetails('2022-04-24T08:15:00.000');
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// => { year: 2022, month: 3, date: 24, hour: 8, minute: 15 }
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```
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## 4. Update an appointment with the given options
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The function will receive first argument as appointment time and second argument of object of some options.
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You have to update the appointment according to the options in the object and return the new appointment date.
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The options object could have multiple options.
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```javascript
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updateAppointment('2022-02-09T09:20:00.000', { month: 6 });
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// => { year: 2022, month: 6, date: 9, hour: 10, minute: 20 }
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```
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## 5. Get the available time between two appointments
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The function will receive two appointments (timestamps) as arguments.
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You have to return the difference between those two times in seconds.
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Because half a second is almost meaningless, round the number before returning it.
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```javascript
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timeBetween('2022-12-12T09:20:00.000', '2022-12-18T08:30:00.000');
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// => 515400
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```
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## 6. Check if an appointment is now valid or not
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Finally, when the appointment is made, the system needs to check if it's valid.
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In other words, the appointment must be in the future, and not the past.
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Write the function `isValid` which takes two arguments, an appointment timestamp (string), and the current time as a timestamp (string) and returns `true` if the appointment is in the future, given the current time.
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```javascript
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isValid('2022-02-11T23:00:00.000', '2022-02-08T23:00:00.000');
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// => true
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```

‎exercises/concept/appointment-time/.docs/introduction.md‎

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# Introduction
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JavaScript has a built-in object `Date` which stores date and time, and provides methods for their management.
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<!-- prettier-ignore -->
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~~~exercism/caution
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It was based on Java's `java.util.Date` class, which was replaced in the early 2010s, but for backwards compatibility, JavaScript's `Date` sticks around.
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Because of how hard it is to work with Dates in general and because of how bad or non-existing timezone handling is, many libraries exist such as `moment.js`, `day.js`, `date-fns` and `luxon`.
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None of these are available on Exercism.
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In your own projects, do not use a deprecated / unmaintained package such as `moment.js` but rely on more modern alternatives like `luxon`, or the not yet widely available [Temporal][mdn-temporal].
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This exercise focusses on `Date`, which will remain relevant until the end of JavaScript.
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~~~
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## Creation
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A `Date` object in an instance of the `Date` class.
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It can be created without passing any arguments to the constructor function.
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This results in a `Date` object that represents the current date and time:
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```javascript
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const now = new Date();
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// => Thu Apr 14 2022 11:46:08 GMT+0530 (India Standard Time)
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// Shows current day, date and time (in your time zone).
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```
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### Unix timestamp (number)
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If a number is passed in, this will be interpreted as a `timestamp`.
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A timestamp is an integer number representing the number of **milliseconds** that has passed since **1 January 1970 [UTC][defn-utc]+0**.
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```javascript
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const epoch = new Date(0);
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// Thu Jan 01 1970 01:00:00 GMT+0100 (Central European Standard Time)
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const another = new Date(1749508766627);
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// Tue Jun 10 2025 00:39:26 GMT+0200 (Central European Summer Time)
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```
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One may expect `new Date(0)` to generate the "earliest" date object, but JavaScript will convert the date to your local timezone, which means that only those around [GMT / with an UTC+0][defn-gmt] timezone will actually get the [Unix epoch][defn-unix-epoch] value.
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### ISO 8601 timestamp (string)
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You can pass a string value representing a date to the `Date` constructor.
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The **only** format that is consistent across implementations is the [simplified version][mdn-date-string-format] of the internationally recognized and standardized so-called [ISO 8601 timestamp strings][defn-iso8601].
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A moment in time at [UTC][defn-gmt] looks like this:
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```text
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YYYY-MM-DDTHH:MM:SSZ
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YYYYMMDDTHHMMSSZ
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```
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Where the following substitutions take place:
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| Key | Description |
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| ---- | ------------------------------------------- |
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| YYYY | The calendar year, represented in 4 digits |
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| MM | The calendar month, represented in 2 digits |
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| DD | The calendar day, represented in 2 digits |
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| HH | The hours in a 24-hour clock, 2 digits |
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| MM | The minutes, 2 digits |
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| SS | The seconds, 2 digits |
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The letter `T` separates the date from the time.
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The letter `Z` indicates UTC (no timezone, no Day Light Savings).
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<!-- prettier-ignore -->
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~~~exercism/caution
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Other formats that are accepted by `Date.parse` may or may not work.
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When working with Dates in JavaScript, _always_ use an ISO 8601 timestamp when converting from a `string` to a `Date`.
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Date-only forms are allowed, but not all ISO 8601 formats are supported.
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Consult the [simplified version explanation page on MDN][mdn-date-string-format].
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~~~
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If the timestamp does not end in `Z`, and it does not end with `+HH:MM` or `-HH:MM`, indicating a timezone offset, because of historical reasons, the following applies:
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> When the time zone offset is absent, date-only forms are interpreted as a UTC time and date-time forms are interpreted as a local time.
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> The interpretation as a UTC time is due to a historical spec error that was not consistent with ISO 8601 but could not be changed due to web compatibility.
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> See [Broken Parser – A Web Reality Issue][ref-broken-parser].
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### Date object
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An existing date object can also be used as a constructor argument.
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This makes a copy of the existing `Date` object with the same date and time.
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```javascript
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const t1 = new Date();
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const t2 = new Date(t1);
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// Values of t1 and t2 will be the same.
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```
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### Supplying individual date and time component values
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A date representing a date can be created by passing three numbers.
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A date representing a date and time can be created by passing in 6 numbers.
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```javascript
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const date1 = new Date(95, 11, 17);
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// Creates Date for Dec 17 1995 00:00 if your local timezone is equivalent to UTC.
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const date2 = new Date(2013, 12, 5, 13, 24, 0);
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// Creates Date for Jan 5 2014 13:24 if your local timezone is equivalent to UTC.
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```
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The second value is the `month`, which starts at `0` for January, up to `11` for December.
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## `Date.parse()`
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You may find mentions of or references to a date parsing function `Date.parse`.
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Because there are only a few invariants (truths) for this function and because the rest of the implementation is not specified (and thus not standard), one should not use it.
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## Accessing `Date` components
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There are various methods on date objects that return the components of the date:
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```javascript
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getFullYear(); // Get the year (4 digits)
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getMonth(); // Get the month, from 0 to 11.
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getDate(); // Get the day of month, from 1 to 31.
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getHours(); // Get the hour in a 24 clock, from 0 to 23
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getMinutes(); // Get the minutes, from 0 to 59
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getSeconds(); // Get the seconds, from 0 to 59
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getMilliseconds(); // Get the milliseconds, from 0 and 999
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getDay(); // Get the day of week, from 0 (Sunday) to 6 (Saturday).
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```
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Each of these has an applicable `set` variant (e.g. `setFullYear`) to update the value.
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Any overflowing value rolls over to the next component:
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```javascript
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const date = new Date('2025-02-28T12:42:00Z');
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// => Fri Feb 28 2025 13:42:00 GMT+0100 (Central European Standard Time)
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date.setDate(29);
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// there was no February 29th in 2025.
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date.getDate();
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// => 1
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date.toString();
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// => Sat Mar 01 2025 13:42:00 GMT+0100 (Central European Standard Time)
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```
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There are UTC variants for all the methods that disregard the local timezone.
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## Converting from date
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Date objects have a method `getTime()` that returns the UNIX timestamp in milliseconds, ie. amount of milliseconds the midnight at the beginning of January 1, 1970, UTC.
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Additionally, a method `toISOString()` is available to convert from a date object to a ISO 8601 timestamp string.
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## Comparing Dates
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Greater than (`>`) and greater than or equals (`>=`) as well as less than (`<`) and less than or equals (`<=`) can be used directly between two dates or a date and a number.
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This works because JavaScript will try to coerce the date to a primitive.
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<!-- prettier-ignore -->
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~~~@exercism/advanced
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When doing a comparison between two dates or date and a number, JavaScript calls [`[Symbol.toPrimitive]("number")`][mdn-to-primitive] which internally calls [`date.valueOf()`][mdn-date-value-of].
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The latter is the same as calling [`date.getTime()`][mdn-date-get-time].
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If you do not want to rely on this behaviour, convert to a number using `getTime()` first.
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~~~
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Dates cannot be compared using equality (`==`, and `===`), but the result of `.getTime()` can.
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[defn-utc]: https://simple.wikipedia.org/wiki/Coordinated_Universal_Time
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[defn-gmt]: https://simple.wikipedia.org/wiki/Greenwich_Mean_Time
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[defn-unix-epoch]: https://en.wikipedia.org/wiki/Epoch_%28computing%29
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[defn-iso8601]: https://en.wikipedia.org/wiki/ISO_8601
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[mdn-temporal]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal
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[mdn-diff-assumed-timezone]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse#differences_in_assumed_time_zone
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[mdn-date-string-format]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date#date_time_string_format
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[mdn-to-primitive]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/Symbol.toPrimitive
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[mdn-date-value-of]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/valueOf
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[mdn-date-get-time]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/getTime
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[ref-broken-parser]: https://maggiepint.com/2017/04/11/fixing-javascript-date-web-compatibility-and-reality/

‎exercises/concept/appointment-time/.gitignore‎

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/node_modules
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/bin/configlet
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/bin/configlet.exe
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/package-lock.json
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/yarn.lock

‎exercises/concept/appointment-time/.meta/config.json‎

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{
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"authors": [
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"SalahuddinAhammed",
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"SleeplessByte"
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],
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"files": {
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"solution": [
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"appointment-time.js"
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],
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"test": [
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"appointment-time.spec.js"
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],
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"exemplar": [
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".meta/exemplar.js"
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]
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},
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"blurb": "Learn how to work with dates by managing appointments",
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"custom": {
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"version.tests.compatibility": "jest-29",
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"flag.tests.task-per-describe": true,
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"flag.tests.may-run-long": false,
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"flag.tests.includes-optional": false
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}
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}

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