To keep time on freelance projects, I use Toggl time tracking software. It's recommended to creatives, but I would suggest it to anyone looking to record time spent. You're able to see reports of total time over periods of a day, week, month and year.  

Toggl can be accessed online, downloaded to offline use or on a mobile device. Simplicity is it's best feature. 

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Insanely simple time tracking. Toggl kills timesheets.
— Toggl