When is the next shmita year? Is there disagreement about which year? If so, which Jewish sects or traditions believe the shmita is in which years? If you specify years since creation, please also specify the timeline with respect to the Gregorian calendar.
The last shemittah year was Jewish year 5768 (13 Sept 2007 - 29 Sept 2008)
The next few are:
Note that some Rishonim (medieval rabbis) held that the shemittah is the year prior to the years mentioned above (See Tur CM 67) but longstanding normative practice is not according to their view.
Source: I remember when everyone was observing the last Shemittah, and it's every seven years after that. I checked Kaluach regarding the dates for Rosh Hashanna.
I thought that the next shemittah will be September 2015, in other words, 7 years after the last Shemittah ended.