Ask HN: How do you keep track of billable hours?

I'm starting next week at a software consulting firm, and I wanted to know your thoughts on strategies is for keeping track of time spent on various clients' projects. A text document? An Excel spreadsheet? An app? What, in your experience, works best for you?

Cheers, and thanks in advance for your advice.

http://www.timetrackturbo.com ...Best I have found so far, easy to use and the developer is easily accessible. (No affiliation, I just use the product)

I use Harvest: http://www.getharvest.com/

If you are joining an existing consulting firm and they don't already have a really good system in place you should probably run screaming in the other direction because that means it's probably a very poorly run firm and not long for this world. Tracking hours and billing efficiently is how you stay in business.

That said, I like the harvest timers (server side state, configurable idle timeout) for the granularity and the fact there is an add-on for the Xero accounting system.

Get yourself a copy of Telestream's Screenflow and record your screen when working. At the end of the billing period, simply scrub through your recordings to build your invoice. Don't mention this to your client as they may request to see them! But if they ever dispute an invoice you'll have no problem winning that battle :-).