as a side note: both ledger [0] and hledger [1] support time tracking/keeping. of all the various tools I tried to use for personal stuff it has been the most convenient one for me (it helps that I also use it for accounting) and I'm using it consequently from day 1 on! you can apply the same reporting/balancing to your time keeping as you do to your accounting.
[0] http://www.ledger-cli.org/3.0/doc/ledger3.html#Time-Keeping