Symbian3/SDK/Source/GUID-B1DD21A3-674A-5193-95CF-F533FDBBD319.dita
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     1 <?xml version="1.0" encoding="utf-8"?>
       
     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
       
     3 <!-- This component and the accompanying materials are made available under the terms of the License 
       
     4 "Eclipse Public License v1.0" which accompanies this distribution, 
       
     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
       
     6 <!-- Initial Contributors:
       
     7     Nokia Corporation - initial contribution.
       
     8 Contributors: 
       
     9 -->
       
    10 <!DOCTYPE concept
       
    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
       
    12 <concept id="GUID-B1DD21A3-674A-5193-95CF-F533FDBBD319" xml:lang="en"><title>Using
       
    13 Date and Time Handling</title><shortdesc>Explains how to manipulate Date and Time.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
       
    14 <p>Points in time are stored and manipulated using the <codeph>TTime</codeph> class. <codeph>TTime</codeph> uses
       
    15 a 64-bit integer to represent time as the number of microseconds since midnight
       
    16 on 1st January 0 AD, using a nominal Gregorian calendar. This gives a possible
       
    17 range of 580,000 years.</p>
       
    18 <p>The date/time and its individual components may be set and retrieved using
       
    19 the <codeph>TDateTime</codeph> class. <codeph>TDateTime</codeph> is the human
       
    20 readable form of <codeph>TTime</codeph>. It is provided to allow easy user
       
    21 access to the year, month, day, hour, minute, second and microsecond components
       
    22 of the time. It does not support manipulation of the date/time, or of its
       
    23 components, but may be converted into a <codeph>TTime</codeph>, and vice versa.</p>
       
    24 <p>Intervals between points in time are represented by the classes derived
       
    25 from <codeph>TTimeIntervalBase</codeph> and by class <codeph>TTimeIntervalMicroSeconds</codeph>.
       
    26 Time intervals can be added or subtracted, either to or from each other or
       
    27 to or from points in time. Time interval classes exist because adding two
       
    28 points in time or subtracting one point in time from another is not possible.</p>
       
    29 <p>The <codeph>Time</codeph> class is a collection of time related utility
       
    30 functions; for example, functions that check for leap years and return the
       
    31 number of days in the month.</p>
       
    32 <section id="GUID-EA8DB5D2-2979-44A9-9D12-AB454050B03E"><title>Arithmetic operations</title> <p>Care should be taken when
       
    33 performing arithmetic operations on <codeph>TTime</codeph> s especially when
       
    34 dealing with the last day in the month. For example: </p> <ul>
       
    35 <li id="GUID-81A3ED23-55B5-5BEF-A2C5-D05458512637"><p>adding one month to
       
    36 October 18th adds 31 days</p> </li>
       
    37 <li id="GUID-CBF68BC9-7F83-5FEC-B5BC-2E63906A5747"><p>adding one month to
       
    38 November 18th adds 30 days</p> </li>
       
    39 <li id="GUID-019F031D-5228-594E-8ECF-9DCAA7C04B09"><p>adding one year to February
       
    40 29th, 1996 gives Feb 28th, 1997</p> </li>
       
    41 <li id="GUID-D019C0F8-9B74-5405-82D4-1ECEB7C3329B"><p>adding one month to
       
    42 March 31st gives April 30th but subtracting one month from April 30th gives
       
    43 March 30th</p> </li>
       
    44 </ul> </section>
       
    45 </conbody></concept>