How to create a chart about a date range if some dates in this range are missing?
I'm assuming you're using the Charts module and that your problem is similar to what is detailed in Comment nr 12 of Issue nr 2052429. Here is part of what that comment includes:


  ... It's not an issue Google Charts could actually fix, as there is no "labels" sent to Google Charts for the chart addons for it to recognise gaps in the data ...


So at a minimum I recommend you to try the most recent DEV version, and apply the patch attached to that comment, to check if that helps in your case. If it doesn't, know that it is a prereq for sure (without that patch you won't be able to get it to work).

If applying the patch is not sufficient, then I'd recommend what's written in the "Bonus tip" of Steps to create charts using the views UI, i.e.:


  You may find it easier to start with a "Table" display and convert it to a chart display after setting up the data. It can be easier to visualize what the result of the chart will be if it's been laid out in a table first.


In other words: before trying to create a chart, make sure the tabular version of it has the correct data displayed.

Disclosure: I'm a co-maintainer of the Charts module (+ author of its community documentation),
I hope this does not violate the site's policy on self-promotion.