você pode usar este código
db.collectin.find({'weekdays.0' : true})
e se quiser verifique 2 dias:
db.collectin.find({$and :
[
{'weekdays.0' : true},
{'weekdays.1' : true}
]
})
db.collectin.find({'weekdays.0' : true})
db.collectin.find({$and :
[
{'weekdays.0' : true},
{'weekdays.1' : true}
]
})