//last day of month
//Date(DateAdd("d",-day(today),DateAdd("m",1,today)))
//First day of year
//date(year(today),1,1)
//last day of month last year
//Date(DATEADD("yyyy",-1,DateAdd("d",-day(today),DateAdd("m",1,today))))
//First day of previous year
//date(year(today)-1,1,1)
therefore
(
[datefield] in date(year(today),1,1) to Date(DateAdd("d",-day(today),DateAdd("m",1,today)))
or
[datefield] in date(year(today)-1,1,1) to Date(DATEADD("yyyy",-1,DateAdd("d",-day(today),DateAdd("m",1,today))))
)