In order to filter dates, one has to create a compute expression, date type, with the following SAQL expression assuming 'foo' is a date field. toDate(foo_sec_epoch). After that, create a filter transformation, check the use SAQL box and enter this in the SAQL filter. date(foo_Year, foo_Month, foo_Day) in ["current fiscal_year" .. "current fiscal_year] (to filter rows at the beginning thru the end of the current fiscal year).
Another sample involves day filters vs year filters> date(CreatedDtOffset_Year, CreatedDtOffset_Month, CreatedDtOffset_Day) in ["29 days ago" .. "current day" ]