only in order to "harvest in 60 days".. actually, the "60 days" is only a rough reference to flowering time under 12/12 lighting. Outdoors, usually matures in late September to mid October, (strain dependant), regardless of "when" you put them outdoors.
Unless you have an auto flowering strain, plants need to go through a vegetative period before they will flower. The 60 days is the flowering period. In acuality, outdoor plants generally take 4-5 months.
If you don't mind setting an alarm clock, ruining your entire social life for three months. You can leave em out 12 and put them in a closet 12. LOL I did it once. 90 day grow LOL PITA too :doh:
I have no life LOL