Going to work early in the morning has many advantages:
1) Less commuting time
Early in the morning streets and trains are not crowded yet and it will take you less time to get to the office. In case you use public transportation you have a much higher chance to get a seat and you can also use the time more productive for reading o learning.
2) No interruptions
Early in the morning there will be few people in the office only. This will allow you to properly plan your day and get the most important things done without being interrupted by visitors, phone calls or new mails.
You are still fresh and concentrated and one hour early in the morning is probably as productive as staying two hours longer in the office in the evening.