The Concept of Time in JavaScript

In JavaScript a time is dened as a Date Object. Each date object stores its state as a time value,
which is a primitive number that encodes a date as milliseconds since 1 January 1970 00:00:00 UTC.
Thus, a date later than 1 January 1970 00:00:00 UTC will have a positive time value, whereas an
earlier date will have a negative time value. On the basis of the common timeline (which we all live
on), the distance between any two dates can be calculated using their time values in milliseconds.
Figure 1 illustrates the concept, where C is a date earlier than 1 January 1970 00:00:00 UTC, and
A and B are later with B being further than A.
1http://www.rio2016.com/en
CSC1401 Assignment 1 Specication { Days-To-Go 2
Figure 1: The Dierence Between Two Date Instances
Functional Requirements
Constants and Variables
Within the script section, create constants and variables following professional conventions and
initialise them using right values. Some constants and variables have been suggested in the following
tables. You should create more when necessary.
Table 1: Constants
Description Value
Number of milliseconds in a day 1000*60*60*24
Number of milliseconds in an hour 1000*60*60
Number of milliseconds in a minute 1000*60
Number of milliseconds in a second 1000
Table 2: Variables
Description Initialising value description Type
Name of the event The name of Rio 2016 Olympic Game String
Year of the event The year of Rio 2016 Olympic Game Number
Month of the event The month of Rio 2016 Olympic Game Number

Day of the event The day of Rio 2016 Olympic Game Number Calculation

1. Create a Date object for the date of the event by using the variables created previously.
Send the object constructor the variables (not values) for year, month, and day of the
event;
Mind the order of arguments sent to the constructor;
Note that month numbers begin at 0 for January, 1 for February, and so on;

2. Create a Date object for the current time.
No arguments need to be supplied to the constructor.

3. Calculate the dierence between the current time and the event time:
CSC1401 Assignment 1 Specication { Days-To-Go 3
Use the getTime() member function to get a Date object's time value in milliseconds
Deduct the time value of current time by using the value of event time.

4. Calculate the number of days to the event:
Divide the time value dierence by the number of milliseconds in a day.
Use the Math.
oor() function to reduce the result number to an integer.

5. Calculate the number of hours, minutes, and seconds in the remaining time value:
(a) Mod the time value dierence by the number of milliseconds in a day;
(b) Divide the mod result by the number of milliseconds in an hour;
(c) Use the Math.
oor() function to reduce the number to an integer for the number of
hours;
(d) Repeat Steps (a) to (c) to calculate the number of minutes and seconds. You may need
to update the calculating formula accordingly.
Presentation
Figure 2: Illustration of the Output
Figure 2 shows a sample output when running the \Days-
To-Go" program. Note that
- the information should be displayed using the alert()
function;
- wherever possible you should use variables in expres-
sions instead of explicit values (e.g., literals and num-
bers), for example, using the variable created for the
event name instead of a string value of \RIO 2016";
- the layout of output may vary depending on web
browsers.
Testing
Test your program by comparing its calculating results to the Days-To-Go feature on the ocial
website of Rio 2016 (http://www.rio2016.com/en). Note that due to dierent locality settings on
your computer and the Rio 2016 server, your calculation result could be slightly dierent from that
shown on the Rio 2016 website. For example, in a test when my program said \521 DAYS" to go,
the Rio 2016 website showed \522 DAYS" { Australia is in almost one day ahead of Rio de Janeiro.
Such a dierence is not an error and is acceptable.
Non-functional Requirements
Structure of the Source Code
- All code should appear in the script section in the head of the HTML document.
CSC1401 Assignment 1 Specication { Days-To-Go 4
- Do not write any code in the HTML body. All functionality are delivered by JavaScript.
- In the script order your code as follows:
(a) Constants;
(b) Variables and objects (declared and initialised);
(c) Other statements.
Comments
- You are required to add at least three comments to the source code.
- Do not comment every single line, instead, comment on blocks of code with a common purpose.
- Do not simply translate the syntax into English for comments, instead, describe the purpose
of blocks of code.
Submission
What You Need to Submit { Two Files
For a complete submission you need to submit two les as specied below. You can submit them
individually or compress them and submit a common .zip (or .rar) le. The assignment submission
system will accept only the les with extensions specied in this section.

1. Statement of Completeness in a le saved in .doc, .docx, .odt, .rtf or .txt format in 200-300
of your own words describes:
- The state of your assignment, such as, any known functionality that has not been
implemented, etc. (It is expected that most people will implement all of the functionality
of this assignment.)
- Problems encountered, such as, any problems that you encountered during the as-
signment work and how you dealt with them;
- Re
ection, such as, any lessons learnt in doing the assignment and suggestions to future
programming work.

2. The program in a le saved with an .html extension contains the source code implemented
following the functional and non-functional requirements.
Late Submission and Extension Request
Please refer to USQ Policy Library - Assessment Procedure for information on the late submission
policy and USQ Policy Library - Assessment of Compassionate and Compelling Circumstances
Procedure for considerable special circumstances in extension request.
The Extension Request Form is available on the course's StudyDesk. Should you need to request
an extension please ll the form and email it to the Course Examiner with supportive documents
(e.g., medical certicate or endorsement letter from supervisor in workplace) prior to the due
date . Please note that any requests without supportive documents will be declined
straigthway without consideration.
CSC1401 Assignment 1 Specication { Days-To-Go 5
Marking Criteria
The assignment will be marked out of 16 and scaled down to a grade out of 8. Table 3 presents the
marking criteria. If all criteria are satised you will receive 16 marks. If not all criteria are met,
part marks may be given. Check your own submission against these criteria before you submit.
Table 3: Marking Criteria
ID REQUIREMENTS MARK
Statement of Completeness
1 The statement is in appropriate length of 200-300 of student's own words 1
2 The \State of assignment" re
ects the true state of completeness 1
3 The \Problems encountered" discusses problems and dealing strategies 1
4 The \re
ection" discusses learnt lessons and reasonable suggestions 1
Subtotal 4
Functional Requirements
5 The program is running without any errors 1
6 All constants and variables are declared and initialised appropriately before use 1
7 The event's Date object is created correctly 1
8 The dierence between two times (the event and now) is calculated using appropriate strategy 1
9 The number of days to go to the event is calculated correctly 1
10 The number of hours is calculated correctly 1
11 The number of minutes and seconds are calculated correctly 1
12 The calculating result is displaying appropriately 1
Subtotal 8
Non-functional Requirements
13 The program has a complete structure including all head, body, script sections 1
dened by appropriate tags
14 Identiers of variables and constants are following professional conventions 1
15 Constants and variables are used in calculation and expression instead of explicit values 1
16 At least three comments are added to describe the purpose of blocks of code 1
Subtotal 4
TOTAL 16