For substracting in moment.js:

moment().subtract(1, 'months').format('MMM YYYY');

Documentation:

http://momentjs.com/docs/#/manipulating/subtract/

Before version 2.8.0, the moment#subtract(String, Number) syntax was
also supported. It has been deprecated in favor of
moment#subtract(Number, String).

  moment().subtract('seconds', 1); // Deprecated in 2.8.0

  moment().subtract(1, 'seconds');

As of 2.12.0 when decimal values are passed for days and months, they
are rounded to the nearest integer. Weeks, quarters, and years are
converted to days or months, and then rounded to the nearest integer.

  moment().subtract(1.5, 'months') == moment().subtract(2, 'months')

  moment().subtract(.7, 'years') == moment().subtract(8, 'months') //.7*12 = 8.4, rounded to 8