I've been at a few companies that required timesheets of software devs, and it was always weird/awkward at best. They never wanted just
hours - they wanted to know what was done as well.
Sometimes it's easy, sometimes it's not, but the thing that bugged me was that it eventually was used against you.
Mgr: "Oh.. well.. I see here you've only put in 38 hours on core projects this last week... this doesn't look too good to others."
Me: "Well, I was actually here in the building for 46 hours, but 8 of those hours were doing some other stuff that there's no timesheet entries for."
Mgr: "Oh... like what?"
Me: "Like answering questions from people in the building that have questions about some of the projects I'm working on - status updates, etc. Apparently you and the other managers aren't updating anyone, and they ask me."
Mgr: "That's not your job."
Me: "So... I should silently ignore them, or give them a canned response to go ask their own dept manager?"
Mgr: "yes. But that didn't take 8 hours last week!"
Me: "I was also doing some research on a couple new debugging tools."
Mgr: "There's no need for that - the senior engineers are making their decision next week about what tool you'll use."
Me: "OK...."
Mgr: "I don't want to see you make a habit of 38 hours a week from now on."
Me: "Ummm... the last 3 months I've been putting in 45-50 hours non-stop, and have been in on some weekends to work with some other people to hit the deadlines."
Mgr: "Yeah, that's great, but 38 hours..."
This is a composite of discussions I've had and colleagues have had with various managers over the years whenever timesheets are involved. YMMV.