Pretty sure the user volume for Uber is higher over the weekends than during the week. Particularly system stressful times are 1:30-2:15am PT on Saturday and Sunday mornings.
Edited out consideration: traffic in your area might be a good proxy for Uber volume. Traffic late at night is generally low.
From personal experience, having driven for Lyft and Uber I'm two cities (Sf, sd) surge in SF does get acutely high in the morning, more broadly in the evening (work departure times are spread out over a wide range of hours), and acute around 2am. In California, bar closures statewide are 2am at the latest, so that accounts for unified departure times in multiple markets.