Default value for date field

I would like the date of subscription be reported in a Community Builder date field. Is it possible ?
If not I could create a date custom field with default value set at the date of subscription (Now). Is it possible and how?

If none is possible I will create a custom date field with a validation rule, I checked, it does not work with validation set at past and future to Now. Can you give me a clue ?

Your product is great !

Kind Regard

I checked with only validate[required,custom[date],past[now]] and it works when subscriber select "today" on the pop-up calendar.
Does it mean the I cannot type validate[required,custom[date],past[now],future[now]] ?