" usually " around 30 days or so. Your autos will sex out first ( throw pistils ) , then transition. They will flower under ANY LIGHT SCHEDULE.
Now is the time to give it as much light as possible , its veg stage is preset and will go up to sexing , THEN it will start a big ass stretch. It will grow rapidly.
If for some reason .... AFTER say Day 40 and nothing is happening THEN DO A FLIP .
Autos are unpredictable .... Even seeds from same stock may show father traits or mother dominate traits. I grew 4 WW autos and 3 were same and one looked like a bush.
Keep feeding your veg nutes up to first week of flower ... This will " load " the plant with enough nitro to carry thru flowering when you switch to bloom nutes.
If you feed bloom nutes to early , plant will yellow up leaves fast looking for that nitro.
Autos are ridiculously easy .... Plug and play. Plant has a prewired life cycle and once they pop they dont stop.