To an extend the bid time on a request, you can do the following:
Opened Requests: Select the request you want to update. Select Actions > Edit. Then select Extend to adjust the close date and time.
Closed Bids: Select the request you want to update. Select Actions > Reopen.
Then adjust the Close Date and either Extend and notify or Extend without notification. Only those yet to submit a bid will be notified.