I haven't checked but this should work .if not please let me know .I am.using my mobile so didn't check it on Tableau . Appology in advance.
I don't know your date format so instead of using any specific date and I m.taking day
if datetrunc ('dayofyear', [Your Date Dimesion / User defined Parameter ) = Today () Function /or Now () and Total(COUNTD(id))>0 then "show" else "Hide" end.
Drag that in filter and select show.Hopw this helps..
PS: Havent tested it #RandomSuggestion
Sent from TypeApp<http://www.typeapp.com/r?b=10647>
Use only Relevant values option in country filter, doing this shows only those countries which has count >0 and also use date=today condition in filter.