At 2am it looks pretty different (which is an odd default right?), at other times it looks pretty much the same. I used 6pm for comparisons and the heat-map was much more similar.

I picked 2am Saturday as the default time because it seemed the most interesting. 5pm Tuesday looks very different. Even 4am Saturday has different hotspots than two hours earlier.

> At 2am it looks pretty different (which is an odd default right?)

Not so odd—especially on a Saturday, I imagine it's right when a lot of people are tipsy or drunk and just want to get home safely, cost be damned.

Which also could be why Tuesday at 2am looks different. Many places are closed on Monday and people are probably less likely to go out.