python - What is the best practice to validate a Django DateField at the model level as particular day of the week? -

i have model:

class mymodel(models.model):     user = models.foreignkey(user)     week = models.datefield() 

my app being built around "weeks ending on saturday", week field accept days saturday.

i'd validation happen in model rather in form, i'm going have data input without form in circumstances.

i understand overriding model's save() method add full_clean() way go, i'm confused best practice here.

what's dryest way?

i go providing validator, if need clean db when inputting data without form.

if input datetime.date, can use mydate.weekday() day of week. should '5' saturday.

something like:

def validate_saturday(value):     if not value.week.weekday == 5:         raise validationerror("date should saturday.") 

an alternative might specify week number in models instead of datefield.