Calculation of duration is 1 second out

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create a new project
2. Create a new task and start it
3. When editing the time manually, occasionally, the overall calculation is 1 
second out, meaning that the finish time must be listed as 07:00:01 to 
counteract the 1 second difference

What is the expected output? What do you see instead?
Accurate calculation of full hours

What version of the product are you using? On what operating system?  Intel
or PPC computer?
1.3.13 on Mac OS X Intel

Please provide any additional information below.

Original issue reported on code.google.com by [email protected] on 12 Nov 2012 at 6:01