Earlier quoted context omitted.
Studies show that deadlines reduce code quality and increase overall time though - so the better solution is to modify the tasks so that "until 15 August" is not part of it.
Any chance you remember what studies? Would love to introduce them to my startup.
I think I read it through HackerNews, pretty sure that Drive points out that time constraints are not a motivator.
Here's a google. http://www.emeraldinsight.com/books.htm?chapterid=17055118
Essentially, time constraints hurt autonomy and therefore creativity. If you have a deadline, you are more likely to find the quickest way that works as opposed to the best error free, scalable long term strategy.