In order to summarise my work for certain projects I use Org's clock tables:

     #+BEGIN: clocktable :maxlevel 2 :scope agenda-with-archives :block 2015-Q1 :tags "ProjectA"  :fileskip0
     #+END:

This summarises the time spent in the first quarter of 2015. However, today I tried to do this for Q3 and it seems to (partially) fail. as you can see below it Org lists the entries of Q4:

    #+BEGIN: clocktable :maxlevel 2 :scope agenda-with-archives :block 2015-Q3 :tags "ProjectA"  :fileskip0
    #+CAPTION: Clock summary at [2015-10-13 di 10:51], for 4th quarter of 2015.
    | File               | Headline             |   Time |      |
    |--------------------+----------------------+--------+------|
    |                    | ALL *Total time*     | *2:08* |      |
    |--------------------+----------------------+--------+------|
    | todo.org           | *File time*          | *1:34* |      |
    |                    | Programming          |   0:36 |      |
    |                    | \_  support forum    |        | 0:36 |
    |                    | Courses              |   0:58 |      |
    |                    | \_  school 2016      |        | 0:58 |
    |--------------------+----------------------+--------+------|
    | todo_ProjectA.org  | *File time*          | *0:34* |      |
    |                    | Financial            |   0:21 |      |
    |                    | \_  Progress reports |        | 0:21 |
    |                    | WP4                  |   0:13 |      |
    |                    | \_  User support     |        | 0:13 |
    #+END:

Changing Q3 to Q2 or Q1 gives the same result. It looks like the calculation of quarters is broken.
I guess this may have to do with my upgrading Org-mode to 8.3 about a month ago.

Did anyone experience this too or is it something with my setup?