SAP system does not know what is broken fiscal year e.g April 2012 to March 2013 and only understand the calendar year. If, for any business, the fiscal year is not a calendar year but the combination of the different months of two different calendar year and then one of the calendar year has to classified as a fiscal year for SAP and the month falling in another year has to be adjusted into the fiscal year by shifting the year by using the sign -1 or +1. This shift in the year is known as the ‘year shift’. Example: April 2012 to Dec 2012 is our first calendar year, and Jan 2013 to March 2013 is our second year, now if you are taking April-12 to Dec-12 as your fiscal year, then Jan-13 to March-13 automatically becomes the second year, and you have to adjust this year by using -1 shift, and vice versa if the scenario is reversed, here you will use +1 shift.