Time interval end points should be exclusive, not inclusive.  This is how ISO8601 defines their standard for time Intervals.  The biggest reason is that if you do it inclusive, you actually end up doing a lot of funky things to get exactly what you want.

Say you want just one day, if it is exclusive, you can say `2014-01-01/2014-01-02`.  If it is inclusive, you have to say `2014-01-01/2014-01-01T23:59:59.999` and *hope* that the lowest granularity possible is a millisecond.  If you happen to have something in nanoseconds, then it's possible that you miss data.  If you do `2014-01-01/2014-01-02` inclusively, you will likely get data for the initial point on January 2nd.