I had a lady wanting to order one of my sticks I am working on which isn't ready yet. So I created custom order listing stating will take 6 to 8 weeks but when made listing I didn't know how to change shipping time so now order is expected to be sent tomorrow and I don't want to get in trouble for not shipping it on time
Go to the three dots next to the order and click Update Ship Date and put in the date you wish to ship it. You cannot do it on the day only before the day so don't wait. You can only do it once.
But it can only be extended by 21 days maximum. To prevent late shipping you may have to cancel and have the customer reorder (set processing to 8 weeks) if you can not dispatch within the next 3 weeks.