Elo rating is pretty fluid, skill levels change depending on time zones, and generally rotate on a weekly and hourly basis. Weekdays UTC-5 5~6 am is usually when it peaks, NA server.

EDIT: What i mean is, over time I've observed that people generally play better at some times and worse at others. For example, people play worse during holidays (It's true: Think of all the drunk gamers at those times). It's not really relevant to gaining elo, but it's just interesting.