How to separate dates store in the same field

I am trying to extract two different dates data store in the same field, depending on a different field...

log.date      lot.type
01/01/2016    open
01/03/2016    closed

What I am trying to do is to put the open date in one column and closed date in a different column, so I can get the duration of time between open date and closed date... thanks for any help.

There are lots way this is possible. But one way that I like to do it is with shared variables.  It works better if you are grouping by something.  So in the details you would have a formula.  One for the open date and one for the closed date (You could eliminate part of the code if you can guarantee the order of the dates). 

The code for each formula would be similar

shared vardate opendate;
if {lot.type} = 'open' then opendate := {log.date};
// This assumes more than two types
shared vardate closeddate;
if (lot.type} = 'closed' then closeddate := {log.date};

then in the group footer you would have a formula for each variable .

shared opendate;  //This will display the date
Then you will have a formula that will do a date diff (I do not know what kind of duration you want).

The date field has a time too, and I am trying to get the duration in HH:MM:SS, from open to close

Thank you for your help, I am going to try it now.

It didn't work... I am not proficient in writing formulas can you explain in detail... and again thank you for your help and patience.   

Opps!!  I wrote the variable declarations wrong.  They should be datevar not vardate.

First you did not explain if you were grouping.  It works pretty well if you are grouping.

The code above (with the if statements) would go in the details section. Then in the group footer you would have a formula similar to below.

shared datevar opendate;
shared datevar closeddate;
diff=datediff( "s",opendate, closeddate);
// convert to string as 00:00:00  will find code later

I get an error message after diff=datediff......
"the remaining text does not appear to be part of the formula"