clear library at one time

[winfredl]

Is there a way to clear your library at one time 

[TomMac]

By day .... pick select, then select all, then delete.

[jguerdat]

It might be worth noting that there's no way to recover deleted videos.  Consider just letting them drop off according to the days supported by your plan so you can go back in time if you need.  Sort of a chintzy recycle bin.