Smoothing acts on days even when option is months

[bmschmidt]

See site here. No smoothing options up to 36 have any effect when the default time measure is a month.

Smoothing parameter seems to be grouping by the number of days (the granularity of the unit, since we represent round to the first of the month and return as that day).

Smoothing when a time parameter ends in _month or _month_year should round by increments of 31 days, not one day. (There are 30.4375 days in the average month, but for behavior to look reasonable with smoothing under 50 months or so, I'm willing to just call it 31).