Calculating the start times for each topic in a presentation

[Peter (Peter Goh)]

Hi, I was wondering how to add the a number to a time? I’m trying to organise a workshop with a number of topics for the morning, with $Duration assigned to each. As this is constantly being changed with the addition and modification of each topic, I was hoping to automate the calculation and display of the start time for each topic.
I’ve tried $EndDate=(($StartDate).format(hh:mm)+time($Duration)); in the rule but have got it totally wrong! Attaching a sample file to hopefully explain what i’m trying to do.
Ideally, I’d like to

1. Assign a start date and time for the session
2. Have that start date be the basis for the start time for topic 1
3. Then have the duration of topic 1 added to it to calculate the end time for topic 1 and then be assigned as the start time for topic 2
   and so on.

Apologies for what must be a very basic question - there’s a reason I stick to my day job!!! Thanks!
Peter
Sample TB.tbx (115.8 KB)

[eastgate]

The easiest approach is to use a date expression. For example:

$StartDate=$StartDate(prevSibling)+"30 minutes";

DateExpression.tbx (86.6 KB)

[Peter (Peter Goh)]

Thanks for this, Mark! And would there be a way I could set the time added from a number attribute $Duration? I don’t seem to be able to do that with $StartDate=$StartDate(previousSibling)+"($Duration) minutes";

[mwra (Mark Anderson)]

@Peter

$StartDate(previousSibling)+"($Duration) minutes";

Try:

$StartDate(previousSibling)+($Duration + " minutes");

Note how we concatenate a Number ($Duration) value and a literal string using parentheses so the that concatenation with $StartDate is that we add a string like "30 minutes). Now we have Date-type data. Used ‘raw’ in a Display Expression we just get a long number string like 1651939560 (why? sup>†):

So, let’s format the Date data for reading on screen using a format string:

($StartDate(previousSibling)+($Duration + " minutes")).format("d MM y t")

Result:

Or, if we start the Display Expression with some text, Tinderbox will correctly guess we want a text version of the date. So, with a $DisplayExpression of:

"Session end:"+"\n"+$StartDate(previousSibling)+($Duration + " minutes")

Result:

But, note that Tinderbox has had to guess how that date info should be described, giving a more complex date string that perhaps we want. So, let us alter the $DisplayExpression to use a formatting of our choice, as tried above:

"Session end:"+"\n"+($StartDate(previousSibling)+($Duration + " minutes")).format("d MM y t")

Result:

More on date formatting codes.

File used for the above: DateExpression-ed.tbx (82.8 KB)

Sorry for long post but I figure a little explanation of the how and why might make the basic answer easier to adapt.

†. Because Date date is simply the number of milliseconds since the Unix epoch(i.e. from a fixed reference date knows to the OS/app). The app then turns that number into human readable dates. But, here, in raw state we just see the number

[Peter (Peter Goh)]

@mwra

date formatting codes

Thanks so much for taking the time to explain the background of this! I love the (slow) discoveries that keep coming up now that I’ve been emboldened by all the videos that you guys are putting out there!
Cheers, Peter