I have not heard that phrase but it probably means the same as "in borad daylight". This means outside in the open where anyone could see. Example: My friend was robbed at gunpoint in broad daylight in front of his hotel.

there is actually no such thing as a Broad Bold day . A old day only exists in our interpretation of reality, which then becomes a self- foretoken and augury. I think broad means indisputable and bold means impressive.

This one is hard because I don´t know the context. I am guessing here but if it is broken down you have broad as wide or large, bold as fearless or daring and day. It might be playing on the expression: In broad day - which means to do something openly (i.e. the thieves went into the bank in broad day not caring that the police could show up at any moment). So maybe it means to be a big fearless day - like a day that someone does something extraordinary. Hope this helps: http://idioms.thefreedictionary.com/in+broad+daylight