@HubMiner Thanks for the hint. Fixed.

More comments are on reddit: https://www.reddit.com/r/openstreetmap/comments/7afo4m/ypids_diary_approaching_1_million_opening_hours/

Also, the slope of opening_hours is ever increasing over time but still pretty stable without many peaks. The only thing that various a bit is the data quality. http://blog.openstreetmap.de/blog/2015/04/wochenaufgabe-oeffnungszeiten/ can be clearly linked to one of the increases in data quality. If someone can explain the other anomalies there, I will be happy to include a hint.

I guess it is not as easy than to line up release dates with the opening_hours stats. Popularity over time of the different way to add and maintain opening_hours would be needed to properly draw conclusions from that which I don’t have.