We should depreciate the "mm" format.
As the simple "mm" format can be quite ambiguous (could just as well be hours), we should recommend "hh:mm". That format also aligns better with the iso standard. --Gorm 15:47, 30 June 2012 (BST)
This tag is recognized at http://map.project-osrm.org/ for ferries. At least the hh:mm format is supported. Proper tagging of duration on ferries ensures that they are chosen where this is natural, instead of choosing a long detour to avoid the ferry.
The OSRM router uses a very conservative speed of 5km/t for vehicle ferries. It is not unusual for large conventional vehicle ferries to have a normal speed of 10-15km/t or more.
OSRM is now supporting ISO8601 format. source:https://github.com/Project-OSRM/osrm-backend/commit/7e00a86bb47dce69913bf27588b73d9a96dce254 Kerosin (talk) 17:25, 2 March 2015 (UTC)
I don't like the format hh:mm because this conflicts with the format for the time of day as used by other keys like opening_hours=* or conditional=*. In order to be consistent, it would be better to use the same format for a duration as specified for maxstay=*. So instead of using <duration=08:00> it would be better to write:
- duration=8 hours
This would even make it possible to use the easily readable 'Time and date' condition, e.g.:
(And no, I don't think using ISO 8601 is a good idea. I suppose that my example in ISO 8601 format would be written like this <duration:conditional=PT5M @ (08:00/18:00); PT7M @ (18:00/19:00)>. The precision is the same but it took me more than 5 minutes to figure this out. My conclusion is that ISO 8601 is not intuitive enough.) --Biff (talk) 23:52, 2 June 2016 (UTC)