People are going to start their working day earlier however grumpy they are. They might need to negotiate with their spouse to re-arrange their pick up and drop off schedule for their kids. Some might need to switch from public transit to car or vice versa since they now have to join the rest of the city in a mad rush to work every morning.
People who starts early are for sure gonna leave early, so the total number of productive hours per day you get from each employee is not going to change. The only thing this changes is how crowded the subway is when you employee leaves the office.
People might start asking, especially the talented ones in your team, why they rejected that generous offer from a competitor last month, so they can enjoy the daily rush hour?
You might ask “Is it really this bad? All they are asking is for people to be on time.” I admit I might have stretched the reaction a bit, however I can tell you in my experience I have seen number of teams dismembers themselves because something small like this eventually snowballed out of proportion. What I am trying to bring out here is not “Don't ask you employee to come early” but rather as a manager before you ask employee to do anything think about what exactly you want to get from your team. As Archimedes famously said, “Give me a lever and I can move the world.” In our little work society mostly governed by Behavioral Economics, everyone reacts to incentives therefore like some economist would like to say “Give me a proper incentive scheme and I can get anyone to do anything”. This may sound arrogant or even devious, however we should not underestimate the power of incentives in our micro-society at work. In my personal opinion everything a manager/leader does is either an incentive which motivates people towards a common goal or negative-incentive which motivates people to work against the common goal.
Lets take a closer look at this particular manager and the problem he is facing. In reality the problem that he is trying to tackle is loss of productivity as well as lacking predictability in project schedule. He is under a lot of stress delivering a major project for the company, but his team had a bad track records of under delivering and schedule overrun in a form of either massive OT or last minute show stopper or both. Thus what he really wants from his team is improved productivity, predictability, and better quality of work. Now if we also take a look at how the team works:
Team works strictly within a waterfall process with no iteration or even intermediate milestone to serve as check points to prevent last minute breakdown
Most of the developers in the team does not practice any form of unit test but rather code by vague design and imagination
There is very limited daily/weekly status meetings of any sort so everyone is working in their own black box with little knowledge of overall progress until its too late
Architect and designer do not code in this team, and all developers are either contractor or outsourced therefore there is an ever-increasing knowledge gap between people who creates design and people who implements them
Its not hard to find many much better incentives that could have worked in team's favor than the 9:30am start time.