Two to three weeks more or less. Ride about 10 miles every other day if possible, or something similar. Mine was excruciatingly painful the first week when I first started riding- then less each time. Now I only get a little in the Spring or after an uunusually long ride- but not terrible anymore.
Expect some sitbone pain every Spring if you have not been riding during the winter- but it'll likely be much less than the very first time ordeal.