Quirky Datetime arithmetic in intraday chart

AFL Programming
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1

In a custom indicator i am developing, I am trying to determine % of trading day remaining- the calculation of which is relatively straightforward - number of secs remaining/ number of seconds in a trading day.

So i am using datetime() function to get the array of the datetime values. Since the trading day starts at 9:15:00 AM, i am using DatetimeDiff() function to calculate the difference between the 2 dates. this works perfectly fine, except, on fridays- (i dont know why??).

I am attaching the code and the trace output for your perusal.

datetime1=DateTime();

for(i=0; i<BarCount; i++)
{
       dtbegin=DateTimeAdd(_DT( DateTimeFormat("%d-%b-%y", datetime1[i])), -885, in1Minute);

       _TRACE(DatetimeToStr(datetime1[i])+ " "+"dtbegin: "+DateTimeFormat("%d-%b-%y %H:%M:%S", dtbegin));

}

and here's the trace output:

10-Jun-20 9:15:59 AM dtbegin: 10-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.11
10-Jun-20 9:16:59 AM dtbegin: 10-Jun-20 9:15:00 AM          Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.11
11-Jun-20 9:15:59 AM dtbegin: 11-Jun-20 9:15:00 AM    	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.15
11-Jun-20 9:16:59 AM dtbegin: 11-Jun-20 9:15:00 AM          Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.15
12-Jun-20 9:15:59 AM dtbegin: 14-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.19
12-Jun-20 9:16:59 AM dtbegin: 14-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.19
15-Jun-20 9:15:59 AM dtbegin: 15-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.22
15-Jun-20 9:16:59 AM dtbegin: 15-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.22
16-Jun-20 9:15:59 AM dtbegin: 16-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.26
16-Jun-20 9:16:59 AM dtbegin: 16-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.26
17-Jun-20 9:15:59 AM dtbegin: 17-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.30
17-Jun-20 9:16:59 AM dtbegin: 17-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.30
18-Jun-20 9:15:59 AM dtbegin: 18-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.34
18-Jun-20 9:16:59 AM dtbegin: 18-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.34
19-Jun-20 9:15:59 AM dtbegin: 21-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.38
19-Jun-20 9:16:59 AM dtbegin: 21-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.38
22-Jun-20 9:15:59 AM dtbegin: 22-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.42
22-Jun-20 9:16:59 AM dtbegin: 22-Jun-20 9:15:00 AM 	Formulas\Custom\IV plotter 22062020 1800.afl	174	105	11:24:05.42

For the sake of conciseness, i have written an if condition to print the first 2 values for a day, so that i can check whats going on across days.

Please let me know what i am doing wrong/ need to change to get my desired output.

Thanks!

Dishant Shah

2

Please follow this advice: How to ask a good question
You need to tell the readers what output do you expect, where do you see something different and why do you think something is "quirky".

3

Ok...so the output for each row in trace should be a datetime value with the date for that particular entry in the array and 9:15:00 am as the time part. The only place where this doesnt happen are fridays for some reason as can be seen in the trace output that i have posted - on 12/6/2020 the value being assigned is 14/6/2020 9:15 instead of 12/6/2020 9:15, same for 19/6 et al. Rest all daysvalue is in sync with the date of that array entry as in for 11/6 it is 11/6 9:15 am, 13/6 it is 13/6 9:15 and so on.

4

hello,
I stopped scratching my head in another thread because the member started off with a very vague description and it wasn't clear what settings/function was even being used.

It appears you might also end up going that way.

looking at your DateTime() output

12-Jun-20 9:16:59 AM dtbegin: 14-Jun-20 9:15:00 AM 
15-Jun-20 9:15:59 AM dtbegin: 15-Jun-20 9:15:00 AM

you are clearly not using AB default settings and this itself will be the cause of a big misunderstanding.
9:16:59 AM this kind of time will only come if you are not using recommended setting.
like Last tick or End-time.
image

Also, i don't understand this.

 dtbegin=DateTimeAdd(_DT( DateTimeFormat("%d-%b-%y", datetime1[i])), -885, in1Minute);

Why are you taking DT, converting to string then back to DT and then subtracting ?

Trying to make up for the interval loss with extra minute(s) is causing you to get new bar of Monday,
and subtracting more than the available time ending with a future date on Friday which is actually a sunday morning.

Also, a better way is to debug using Exploration, put each variable in a column and check the output. As in tabulate it properly.

so kindly get all the stuff right because as i said, manipulating non-default settings will require the user to understand Amibroker properly.

5

Hi,

Thanks for your response. I will answer your queries one by one.