This isn't going to help, but I just tried this with Lazarus SVN (which I assume is darned close to 1.0.12), and then Lazarus 1.0.8 using trunk Lazarus-CCR zvDateTimeCtrls, and it worked for me both times I'm afraid...
Here's the steps I followed...
Package - open Package File (.lpk)
Navigate to ...\lazarus_ccr\components\ZVDateTimeCtrls\trunk. Opened "zvdatetimectrls.lpk"
On the Package Manager Diag, Hit Compile, then Use - Install. Answered Yes. Laz re-compiled, re-started and the controls are in a tab called "Date and Time Ctrls" right at the end...
Sigh - perhaps my SVN ~ 1.0.12 assumption isn't valid - downloading now...
Update: Nope, no change under 1.0.12, works fine for me.
Further info: my SVN and 1.0.12 were 64 bit. 1.0.8 was 32 bit... And I'm also Win 8, 64bit. Guess I'm going to need to update my sig now :-)
You doing anything different to the above? If so, let us know. I'm not sure where the "Rebuild Many" bit comes in for instance, I certainly never saw anything like that.