Set unchecked DateGadget value to -1, please.

[es_91]

The Doc says:

If you specify #PB_Date_Checkbox in the Flags parameter, the Gadget will have a checkbox with which the user can set the Gadget to 'no date' [...]. While the checkbox is unchecked, GetGadgetState() will return 0. To change the state of the checkbox, use SetGadgetState() with either 0 (=checkbox unchecked) or any valid date.

Since '0' is a valid date, and the usual date error code is '-1', why not use '-1' for an unchecked DateGadget?

[chris319]

This is a good idea.