9v battery to supply voltage?

[exibar]

How long do you think a regular 9volt battery would last powering this clock? I'd like to hide the battery for a project, and don't really want to use 6 D or C cells.... or maybe use 6 D cells and a 9v battery in parallel to keep the 9v battery powering the clock if the D cells are removed..... but for how long will a 9volt battery power the clock?

this will be for a boy scout Military Spy type event :-)

thanks all!
Mike B

[Michael]

A 9V will last only 2 or 3 hours I think.

[exibar]

2-3 hours will be cool... I can double the time by putting them in parrallel, that's perfect!