AdWords Hour of Day
This report lets you view statistics by hour of the day (00:00/12:00 AM - 23:00/11:00 PM) and by day of the week (0/Sunday - 6/Saturday) based on the time-zone settings for the relevant view.
If you're selling a service or product within a particular region or country, it may be advantageous to target your ads to specific hours of the day and/or to specific days of the week. If you're selling worldwide, targeting specific times may be less of a concern because it's always noon or five o'clock somewhere.
For example, if you're selling packaged family vacations to popular theme-park destinations, you may want to run your ads more heavily from 11 AM to 1 PM when parents are apt to break for lunch, again at the end of the work day from 4 PM to 6 PM, and maybe from 9 PM to 11 PM after the kids are in bed. If you're selling an insomnia remedy, you might want to target 1 AM to 4 AM.
Or if you're an app developer trying to drive downloads of a new game, you might want to target days and times when people are likely to be on their cell phones, such as morning and evening commutes on weekdays, weekday evenings, and all day on weekends.
If you have assumptions about which times and days are best suited to your purposes, you can target those times with your ads and then test your assumptions with the information in this report. Alternatively, you can begin by running the same frequency of ads during all hours and days, and then use this report to see which are most effective and then shift your resources there.
You can sort by Avg. Session Duration or Goal Completions to see whether there are parts of the day that draw more engaged users. If you find, for example, that users between 6 PM and 9 PM tend to spend more time on your site or app and complete Goals more readily, you can bid more during those hours.
You can also do things like add Keyword as a Secondary Dimension and sort by Revenue to see whether particular keywords are more effective during different parts of the day.