How long did it take you to go into labor when...

I know everyone's labor is different but I am just curious. I went to my weekly doctors appointment yesterday and I was 4 cm dilated and stretchy she said already. I am a first time mom and 38 weeks today. She said I could go into labor anytime now, and if I don't either way I am getting induced on the 15th in 6 days to have him on the 16th to have him on Wednesday. How long did it take y'all to go into labor then?