Question: We're creating a chart showing traffic by time of day over a given period. So the y-axis is traffic, the x-axis is midnight, 1am, 2am, etc. It could also be days of the week. What's the generic name for this type of chart? I've come up with "cycle chart". Is that the standard? Is there one?
![example](https://i.stack.imgur.com/IDu3k.png)

Update:

Just to add a bit more clarity, what's being shown in the top chart is *not* one day, it's an aggregation of many days. E.g. over the last month, 6am has on average been lower than noon. Similarly, in the bottom chart, over the last year, traffic dips on Saturdays.

Answer: 
I'd suggest "diurnal" or "circadian" rhythm chart. For weekly, the latter would be "circaseptan", "circamensual" for "monthly", and "circannual" for "yearly".
The type of chart you've drawn is known as a Histogram <http://en.wikipedia.org/wiki/Histogram>