Managed C++/CLI

Working with date_t and time_t

10-Oct-16 21:53

Why have you posted this under Managed C++?

for study23-Sep-16 22:13

23-Sep-16 22:13

I am receiving a date structure in "24-9-2016 13:30" format. Now I want to convert time value to specific timezone, I am doing calculations and have number of hours to add or substract.

So I don't know: how can I initialize tm struct with the date value I have? how to add or substract hours in tc struct variable to get required date?

my intention is
Date received "24-9-2016 13:30" and 5 Hours to add so final Date: "24-9-2016 18:30"

C++

//Temporarily init time to local
time_t tempTime
time(&tempTime);
struct tm *initStruct = localtime(&tempTime);//initialize it with local time
//now modify it to user defined date
initStruct ->tm_year = 2016;
initStruct->tm_mon = 9;
initStruct->tm_hour = 13;
.
.
.
 //Not sure how can I subtract or add hours in this struc to get desired date value

please provide inputs.

modified 24-Sep-16 4:55am.

Richard MacCutchan23-Sep-16 22:53

23-Sep-16 22:53

I am not sure what this has to do with Managed C++. However, the time, _time32, _time64[^] function describes the content of a time_t value, which you can easily initialise with a user defined time. I have not come across a date_t type, where is it defined?

for study23-Sep-16 22:59

23-Sep-16 22:59

Sorry, if I used wrong group to post. I have updated post with some of the steps I tried, please check and let me know if is there any solution available.

Richard MacCutchan23-Sep-16 23:05

23-Sep-16 23:05

Since all those fields are integers you can add, subtract or replace any of them. You should check that the values are valid in terms of the calendar, although the mktime, _mktime32, _mktime64[^] functions will attempt to normalise a tm structure into a valid time. There are many other useful functions, and you should study the documentation to see which ones will help you.

for study23-Sep-16 23:33

23-Sep-16 23:33

Yes, all these are integers, so I can perform addition or subtraction, but it is not handled well in below cases-
if hours are added
Like 4.5 then 13 hours should become 18:30
Or more than 24 then date should modify

In above cases I will need to add additional code depending on hours value, which is bad, isn't there any system method which will modify entire structure depending on the value assigned

Richard MacCutchan23-Sep-16 23:58

23-Sep-16 23:58

If you want to add partial hours, days etc. Then use mktime (as I advised in my previous comment) to convert your tm structure into a time_t value. you can then just add or subtract the number of seconds in your time increment.

for study24-Sep-16 0:11

24-Sep-16 0:11

ok, so here is what I did now-

C++

//Temporarily init time to local

time_t tempTime
time(&tempTime);
struct tm *initStruct = localtime(&tempTime);//initialize it with local time
//now modify it to user defined date
initStruct ->tm_year = 2016;
initStruct->tm_mon = 9;
initStruct->tm_hour = 13;
//completed it...

int hoursToAdd = 4.5;

initStruct->tm_hour = initStruct->tm_hour + hoursToAdd;

time_t myTime = mktime(initStruct);//this return -1

printf( "%s", ctime( &myTime));//this prints null..

any idea whats going wrong here?

Richard MacCutchan24-Sep-16 0:29

24-Sep-16 0:29

C++

int hoursToAdd = 4.5;

That is not a valid statement so it will not even compile. You cannot assign a floating point number to an integer variable.

for study24-Sep-16 0:37

24-Sep-16 0:37

Yes, my bad. well in that case my original question reopens how can I assign partial hour to tm struct to enable it to give valid date value.

Richard MacCutchan24-Sep-16 0:48

24-Sep-16 0:48

You really (and I mean really) need to go and study the documentation which explains what each field represents. If you have some number of hours and some number of minutes then you need to add them separately to each field. You should also step through your code with the debugger so you can see at each step what are the values of the various fields.

for study25-Sep-16 19:18