[{"availability_detail":{"daily_schedule":{"start_time":"03:00","end_time":"04:00"},"on_days":["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"]}},{"availability_detail":{"on_days":["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"]}},{"availability_detail":{"daily_schedule":{"start_time":"00:00","end_time":"04:00"},"on_days":["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"]}}]

db.collection.aggregate([{$match:{$or:[{"availability_detail.daily_schedule":{$exists:false}},{$expr:{$lte:[{$toInt:{$concat:[{$arrayElemAt:[{$split:["$availability_detail.daily_schedule.start_time",":"]},0]},{$arrayElemAt:[{$split:["$availability_detail.daily_schedule.start_time",":"]},1]}]}},0]}}]}}])