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<concept id="GUID-B1DD21A3-674A-5193-95CF-F533FDBBD319" xml:lang="en"><title>Using

Date and Time Handling</title><shortdesc>Explains how to manipulate Date and Time.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>Points in time are stored and manipulated using the <codeph>TTime</codeph> class. <codeph>TTime</codeph> uses

a 64-bit integer to represent time as the number of microseconds since midnight

on 1st January 0 AD, using a nominal Gregorian calendar. This gives a possible

range of 580,000 years.</p>

<p>The date/time and its individual components may be set and retrieved using

the <codeph>TDateTime</codeph> class. <codeph>TDateTime</codeph> is the human

readable form of <codeph>TTime</codeph>. It is provided to allow easy user

access to the year, month, day, hour, minute, second and microsecond components

of the time. It does not support manipulation of the date/time, or of its

components, but may be converted into a <codeph>TTime</codeph>, and vice versa.</p>

<p>Intervals between points in time are represented by the classes derived

from <codeph>TTimeIntervalBase</codeph> and by class <codeph>TTimeIntervalMicroSeconds</codeph>.

Time intervals can be added or subtracted, either to or from each other or

to or from points in time. Time interval classes exist because adding two

points in time or subtracting one point in time from another is not possible.</p>

<p>The <codeph>Time</codeph> class is a collection of time related utility

functions; for example, functions that check for leap years and return the

number of days in the month.</p>

<section id="GUID-EA8DB5D2-2979-44A9-9D12-AB454050B03E"><title>Arithmetic operations</title> <p>Care should be taken when

performing arithmetic operations on <codeph>TTime</codeph> s especially when

dealing with the last day in the month. For example: </p> <ul>

<li id="GUID-81A3ED23-55B5-5BEF-A2C5-D05458512637"><p>adding one month to

October 18th adds 31 days</p> </li>

<li id="GUID-CBF68BC9-7F83-5FEC-B5BC-2E63906A5747"><p>adding one month to

November 18th adds 30 days</p> </li>

<li id="GUID-019F031D-5228-594E-8ECF-9DCAA7C04B09"><p>adding one year to February

29th, 1996 gives Feb 28th, 1997</p> </li>

<li id="GUID-D019C0F8-9B74-5405-82D4-1ECEB7C3329B"><p>adding one month to

March 31st gives April 30th but subtracting one month from April 30th gives

March 30th</p> </li>

</ul> </section>