Hi

I've noticed that when you use 'today' as the last parameter in the 'date' url parameter that it responds with one extra date in the array (the day before the start date).

Example:
http://demo.piwik.org/?module=API&method=VisitsSummary.getVisits&idSite=3&period=day&date=2014-09-01,today&format=json

Returns

{
"2014-08-31": 18,
"2014-09-01": 23,
"2014-09-02": 17,
"2014-09-03": 28,
"2014-09-04": 19,
"2014-09-05": 29,
"2014-09-06": 17,
"2014-09-07": 19,
"2014-09-08": 23,
"2014-09-09": 17,
"2014-09-10": 20,
"2014-09-11": 12
}

I requested the dates starting from 2014-09-01, but it included the previous day as well.

But when I manually enter the end date, it seems to return the dates just fine.

Example:
http://demo.piwik.org/?module=API&method=VisitsSummary.getVisits&idSite=3&period=day&date=2014-09-01,2014-09-11&format=json

Returns

{
"2014-09-01": 23,
"2014-09-02": 17,
"2014-09-03": 28,
"2014-09-04": 19,
"2014-09-05": 29,
"2014-09-06": 17,
"2014-09-07": 19,
"2014-09-08": 23,
"2014-09-09": 17,
"2014-09-10": 20,
"2014-09-11": 12
}

I found this bug on our servers running Piwik 2.6.1, as well as on the demo Piwik running 2.6.1 (see example URLs) and it's reproducible on every API call.

If you need more information, feel free to ask.