Had never seen this before -- but I don't use too much from FEX routinely (and seem to never think about searching), so that's not surprising.
However, this is quite old and is based on using the old and klunky datetick function associated with the venerable datenum date type; not certain about what it would do with datenum if you used it instead.
One thing I notice is that your first format string is all lower-case; datetick format strings are not the same as those for datetime; the time portion should be UPPERCASE as HH:MM instead of lowercase hh:mm. What this does internally I don't know, either, but is not correct for datetick
I would suggest first converting to datetime from datenum and replotting; the plot functions now are datetime aware and you'll get rescaling on zoom automagically -- and if don't get precisely the format desired, change the axes date format string easily as an axes property instead of having to reissue a datetick instruction as before or use such a workaround as this.
While looks to have been a nice piece of work and served a function, I think it's been made obsolete with datetime class.
