No best time but maybe best luck

Before buying do some research to know the company, industry, potential growth blab blab blab and there is no best time. Investment is a a gamble. If there is a best time for Sure Win there will be no more people working. Sometimes Luck plays a part in investment.
Selling is no brainer. When it reaches your target profit, sell and run. Important to note can't be greedy as it can end up either way-earn more or lose big.

Happy investing/gambling .