I am not sure I am asking at the right place, if not, please point out where should I write this.
Last survey from OSMF Board about OSMF membership refers to “the number of calendar days on which a person has edited the map”. I understand the words, but I fail to understand the meaning of the metric.
Say someone made literally one change, like added smoothness to the road and that’s it. Is it one day of edits? Is this the same calendar day when somebody spent 12 hours non-stop of editing?
Yes, that’s exactly what it means. Both of these examples are 1 calendar day of editing.
And clearly, this is not a good metric if the goal is to compare how much two people have contributed to OSM. It’s easy to find examples where someone has contributed much more than someone else, yet it took them fewer days to do so. However, we can come up with similar examples for the other potential metrics as well (such as number of changesets, edited elements, or edited tags), so I suspect that any automated assessment of OSM contributions is inherently flawed. And then there’s the problem of contributing to OSM by means other than mapping, e.g. organizing mapping parties or writing software…
But the way I see it, that’s doesn’t mean the membership prerequisites cannot work. Their goal is just to ensure a basic level of familiarity with OSM. This means they’re intentionally a low bar that’s not too hard to pass. And if nothing else, having been active on a number of calendar days means that the person has mentally engaged with OSM on a regular basis, and that their involvement with OSM has continued over some period of time.
That being said: If you do agree that contributions should be a prerequisite for membership, but prefer a different metric for counting contributions, please mention this in the survey (or in discussions such as this one).
And sorry for the mess that was caused by a moderator merging your post into an existing thread and me attempting to undo that. Your post is a perfectly fine way of raising this question.
Thank you very much for your answer and helping organizing my question.
As for this metric I have really hard time to decide, on on hand I am all pro such measure, but on the other hand in my opinion it would be better to have no metric at all than flawed metric.
So I am just thinking aloud, let’s say we set or 21 days, and let’s say such person starts the same way as me, half a day editing once a week. After 10 weeks (10 calendar days of actual work) such person consider membership and hears – 21 days (weeks for him/her). It is about half a year, and in my case it would be 2 years of waiting period. So someone could come to conclusion, “wait a second, this is crazy, if my work is not enough, and I have to work so hard, this entire OSM are crazy people” 
On the same time, some other person, taking his/her time, and making less effort, just make a change here and there every evening.
So I see this metric as flawed – it gives the wrong impression and forces people into artificial scheduling of their edit just to meet the criteria.
The other would be number of changes – this is way more fair (IMHO). And maybe even better, that say candidate should have N changes of K categories (category – editing road shape, changing/adding road features, adding/updating amenities).
In both cases I am only afraid of acts of vandalism just to get the right score, like edits, commits, cancel-edits, or splitting roads which is very easy to do (this could be ruled automatically, I am just pointing out as general example).
For any metric trying to measure the “engagement” to OSM there will be examples where this metric leads to totally absurd results.
IMHO if a metric is chosen it should be as simple as possible and not pretending to be an almost perfect measure.
Days of mapping are in this sense easily understandable even by people not familiar with change sets, tags, values, points, history etc etc.
Main objective of this survey is to get a feedback if there should be an minimum acquaintance with OSM before being accepted as OSMF member and what the limit should be.
Just a small note, the board is not proposing ‘mapping days’ it is proposing mapping mesured in UTC days (and yes it makes a difference).
Indeed. For example someone uploading a few changesets in the evening in the Americas could find themselves earning 2 editing days if these changesets happen to fall before and after 0:00 UTC.