Absolute minimum remaining time to revise the end an item I'm selling

[gransestate4068]

I want to end my listing tonight ASAP.,There's no bids. Is there a restriction on how quickly we can make the new end time. Or do we need to select a new end time from the pre-set number of days, eg 5 days etc. We do not want to 'remove' the listing but rather just have it ending before we are away and out of Internet service for a few days.