This question could be answered in many ways ... but the answers may not be what one expects.
One way of answering this question is from the traditional training metrics point of view – we did 20 days per employee of classroom training last year, and so we should do the same thing this year too.
But here’s a problem with that approach: is your market situation this year, the same as it was last year? Is your company going to sell the same products or services to the same people in the same way this year, as it did in the last? And is it going to produce those products or services the same way this year, as in the last?
The simple answer to all these questions: Probably not.
Then, why should the ‘number of training days’ for this year bear any connection to the previous year’s figure?
'Training' is a part of 'Learning', which ought to be tightly linked to organisational strategy. If you could articulate the strategy, business needs and performance needs of your company, a Learning consultant might be able to boil that down to 'number of training days per employee' for the current year, after an appropriate Learning strategy, plan and the Learning events calendar have been created.
This number could vary significantly between industries, companies and from year to year, because every company's strategy is different, and evolves from year to year.
To quote a parallel: “What is the minimum number of days companies take to achieve their targets?”
Well, doesn’t that depend on which company, what target and when?