A:

In the days of FP5 the EU set (although some exceptions were allowed for individual countries/projects) maximum annual productive hours as 1,680, or an average of 140 hours per month. This is equivalent to 17.5 productive days per month for an 8 hour day.

In truth the basis for each organisation should be set by that organisation by taking the employees' average annual hours (i.e. excluding non-productive hours e.g. sickness, holidays, maternity leave, lunch breaks etc), dividing that by 12 to arrive at the average per month and then by 8 (or normal working day length in hours). We would be surprised if this is far different from 17.5, and certainly 20 looks excessive.

17.5 productive days per month on average is a good guidance figure for FP6, but it is not compulsory.