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.
The shmittah years listed above are wrong. The timeline has been lost and incorrectly started again.
The shmittah year was celebrated the year that Herod the Great laid siege to Jerusalem, in the year [Siege of Jerusalem (37 BC)]https://en.wikipedia.org/wiki/Siege_of_Jerusalem_%2837_BC%29 "The besieged suffered from lack of provisions, compounded by a famine brought about by the sabbatical year"
The Civil year would have started in the Fall, and would have been 38 to 37 BCE. The siege started in the spring 37 BCE, and was over before the year was expired, and it was particularly a severe siege since it was also a shmittah year. This was a 7th shmittah or 49th year, with the following year 37 to 36 BCE being the Jubilee year 79th. www.torahcalendar.com/Calendar.asp?YM=Y-37M7
Now add 50 years for each Jubilee Cycle and you get [14 to 15 CE as the next Jubilee year 80th.]www.torahcalendar.com/Calendar.asp?YM=Y14M7
There is no year zero, so 1BCE to 1 CE is just 1 year. Add 40 more Jubilee years and you have 2000 more years, and it is [Jubilee year 120, 2014 to 2015 CE.]www.torahcalendar.com/Calendar.asp?PYM=Y2014M7
So .... [2013 to 2014 CE] our present year is:
Civil Year 5999
Year 7 in Shemittah Cycle 7
Creation Shemittah Cycle 840
Year 49 in Jubilee Cycle 120