coding of datedifference

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i am working on library management software
so i need the difference of date between date on which book is issued and date on which book is returned so that i can calculate fine.
both date should be taken from system directly,not from user side.so i need a code.

Posted 23-Jun-12 0:30am

ismile92

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4 solutions

Solution 1

Then you can use the GetSystemTimeAsFileTime[^] function.

FILETIME is a struct, but you can use an __int64 since the memory layout matches.

__int64 currentDateAndTime;
GetSystemTimeAsFileTime((LPFILETIME)&currentDateAndTime);

SYSTEMTIME systime;
FileTimeToSystemTime((LPFILETIME)&currentDateAndTime,&systime);

Doing the calculations on an __int64 is pretty easy ...

Convert to SYSTEMTIME[^] when you need to access the various elements of the date and time information.

Best regards
Espen Harlinn

Posted 23-Jun-12 1:04am

Espen Harlinn

Updated 23-Jun-12 2:41am

v2

Comments

Sandeep Mewara 23-Jun-12 10:01am

5! Good answer.

Espen Harlinn 23-Jun-12 10:03am

Thank you, Sandeep :-D

Richard MacCutchan 23-Jun-12 10:39am

Why not just use the simple functions - see my amended response.

Espen Harlinn 23-Jun-12 10:48am

No reason at all, using time and difftime is a portable solution. :-)

For work, that is things I get paid for, I combine this solution, that is my, with your initial solution. Implementing classes similar to System.DateTime and System.TimeSpan is a fairly straight forward operation based on using an __int64.

Solution 3

You did not specify whether it is for MFC C++ or something else, so here's the MFC version of it...

1. Get date/time when the book was issued:

C++

CTime bookIssued = CTime::GetCurrentTime();

2. Get date/time when the book was returned:

C++

CTime bookReturned = CTime::GetCurrentTime();

3. Calculate the difference in days:

C++

CTimeSpan diff = bookReturned - bookIssued;
__int64 days = diff.GetDays();

Your variable days now has the number of days that you need.

Posted 23-Jun-12 4:36am

Vitaly Tomilov

Updated 23-Jun-12 4:38am

v4

Solution 4

The boost date/time library Boost date/time[^] works really well and it's portable. It's pretty extensive and fearsome but the Date and Date Duration sections are all you need.

Posted 23-Jun-12 7:26am

Aescleal

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Richard MacCutchan · Accepted Answer · 2012-06-23T03:45:00

Solution 2

~~Read up on System.DateTime[^] and System.TimeSpan[^].~~

[edit]
As Espen & Vitaly pointed out this is a C++ question so my answer is not relevant, sorry. However using the time()[^] and difftime()[^] functions of the CRT library you can achieve the same objectives.
[/edit]

Posted 23-Jun-12 3:45am

Richard MacCutchan

Updated 23-Jun-12 4:38am

v2

Comments

Espen Harlinn 23-Jun-12 10:03am

5'ed! that's how to do it if he is using C++/CLI :-D

Vitaly Tomilov 23-Jun-12 10:09am

Irrelevant to C++.

Richard MacCutchan 23-Jun-12 10:34am

Oops!