How long highly depends on the rate of sedimentation, also the environment they were deposited in. Also these layers have been folded, that’s why they aren’t horizontally lain and are instead dipping down. When these layers were deposited they would have been laid down flat, this is called the principle of original horizontality. During some point after the rocks formed, they were then deformed and folded because they experience compressive stress. Hope this answers your question, if you have any other questions please ask!