1. Working with Date
ISYS 350

2. Java Date Processing: Date Class
Define a date object:
Date myDate;
Define a date object with the current date:
Date currentDate = new Date();
getTime method: return the date in milliseconds since 1/1/1900
Note: A day has 24*60*60*1000 milliseconds.

3. Java Date Processing: DateFormat class
DateFormat class is used to define a date format to display a date object or parsing a date/time string to create a date object.
Define a date format:
DateFormat formatter = new SimpleDateFormat("MM/dd/yy");
To print a data object:
out.print("Current date is: " + formatter.format(currentDate));
To parse a date string:
myDate=formatter.parse(request.getParameter("txtDate"));

4. Import Java Class Example: Display Current Date Time
Import java.util.Date
import="java.util.Date"%>
Define a Date type variable:
Date currentDate = new Date();
Display in textbox using JSP expression:
<p>The time is: <input type="text" name="num2" size="20" value="<%=currentDate%>"></p>

5. Date Format Import class: Define a format:
import="java.text.DateFormat"%>
Define a format:
SimpleDateFormat formatter = new SimpleDateFormat("MM/dd/yy");
Convert:
Example: Display a date with date format:
String displayDate = formatter.format(currentDate);
<%
Date currentDate = new Date();
SimpleDateFormat formatter = new SimpleDateFormat("MM/dd/yyyy");
String displayDate = formatter.format(currentDate);
%>
<p>The time is: <input type="text" name="num2" size="20" value="<%=currentDate%>"></p><br>
<p>The time is: <input type="text" name="num2" size="20" value="<%=displayDate%>">

6. Define Date Format
Letter   Date or Time Component   Presentation       Examples G        Era designator              Text                AD y        Year                        Year                1996;    96 M        Month in year                Month               July; Jul; 07 w        Week in year                Number               27 W        Week in month                Number               2 D        Day in year                Number               189 d        Day in month                Number               10 F        Day of week in month        Number               2 E        Day in week                Text               Tuesday; Tue a        Am/pm marker                Text               PM H        Hour in day (0-23)        Number               0 k        Hour in day (1-24)        Number               24 K        Hour in am/pm (0-11)        Number               0 h        Hour in am/pm (1-12)        Number               12 m        Minute in hour            Number               30 s        Second in minute            Number               55 S        Millisecond                 Number               978 z        Time zone                   General time zone   Pacific Standard Time; PST; GMT-08:00 Z        Time zone                  RFC 822 time zone   -0800

7. Calculating Days between Current Date and Entered Date Using the getTime() method
<form name="dateForm" method="get" action="computeDate.jsp">
Enter a date: <input type="text" name="txtDate" /><br><br>
<input type="submit" value="compute Date" name="btnSubmit" />
</form>

8. computeDate.jsp <% Date currentDate = new Date(); Date myDate;
DateFormat formatter = new SimpleDateFormat("MM/dd/yy");
myDate=formatter.parse(request.getParameter("txtDate"));
out.print(currentDate +"<br>");
out.print("Current date is: " + formatter.format(currentDate)+"<br>");
out.print("Entered date is: " + formatter.format(myDate)+"<br>");
out.print ("Days between = " + (currentDate.getTime()-myDate.getTime())/(24*60*60*1000)+"<br>");
DateFormat yearFormat=new SimpleDateFormat("yyyy");
DateFormat monthFormat=new SimpleDateFormat("MM");
DateFormat weekDayFormat=new SimpleDateFormat("E");
DateFormat hourFormat=new SimpleDateFormat("H");
out.print(yearFormat.format(currentDate)+"<br>");
out.print(monthFormat.format(currentDate)+"<br>");
out.print(weekDayFormat.format(currentDate)+"<br>");
out.print(hourFormat.format(currentDate)+"<br>");
double hour;
hour=Double.parseDouble(hourFormat.format(currentDate));
%>