I think the template would benefit from a more elaborate Period measure -- something like this:
Period =
-- Parameters
VAR IsDMY = TRUE()
VAR DayFormat = "d"
VAR MonthFormat = "MMMM"
VAR YearFormat = "yyyy"
VAR LabelText = UNICHAR ( 128197 ) & " "
-- Formats
VAR DayMonthFormat = IF ( IsDMY, DayFormat & " " & MonthFormat, MonthFormat & " " & DayFormat )
VAR FullYearFormat = IF ( IsDMY, " ", ", " ) & YearFormat
VAR FullDateFormat = DayMonthFormat & FullYearFormat
-- Input dates
VAR MinDate = MIN ( 'Date'[Date] )
VAR MaxDate = MAX ( 'Date'[Date] )
-- Formatted dates
VAR StartDate = FORMAT ( MinDate, FullDateFormat )
VAR EndDate = FORMAT ( MaxDate, FullDateFormat )
VAR StartDay = FORMAT ( MinDate, DayFormat )
VAR EndDay = FORMAT ( MaxDate, DayFormat )
VAR StartMonth = FORMAT ( MinDate, MonthFormat )
VAR EndMonth = FORMAT ( MaxDate, MonthFormat )
VAR StartYear = FORMAT ( MinDate, FullYearFormat )
VAR EndYear = FORMAT ( MaxDate, FullYearFormat )
VAR StartDayMonth = FORMAT ( MinDate, DayMonthFormat )
VAR EndDayMonth = FORMAT ( MaxDate, DayMonthFormat )
-- Result
RETURN
LabelText &
SWITCH (
TRUE(),
-- Only one day is selected
StartDate = EndDate,
EndDate,
-- Dates fall within the same month
AND ( StartMonth = EndMonth, StartYear = EndYear ),
IF (
IsDMY,
StartDay & "–" & EndDayMonth,
StartDayMonth & "–" & EndDay
)
& EndYear,
-- Dates fall within the same year
StartYear = EndYear,
StartDayMonth & " – " & EndDate,
-- Dates in different years
StartDate & " – " & EndDate
)
I think the template would benefit from a more elaborate Period measure -- something like this:
More details, including the description of parameters and the measure in action, can be found here: http://community.powerbi.com/t5/Quick-Measures-Gallery/Date-range/m-p/365203