when

Hi All. I am outdoors in South Africa. It is now December and the season ends in March or April. Shouldn't my plants be giving some indication of sex by now? A few have switched to alternative growth from opposed growth. I have read that in 2 months you should be able to Pre sex Perhaps...

Just from wondering through forums and stuff I have seen many people saying that their plants are, for example, a week away from being done. Is this a estimation from the physical apparence of the bud or is it a predetermined finishing date? How do you know when your "harvest is ripe" and ready...