For me the best time to invest is when you know or learn the value of bitcoin, when it come to drop and up time to time. Like now btc is up and some theory it become high and high if the month of june.
well it is high time for investing in btc now as more people already witnessed how the price of bitcoin skyrocketed and that gave people a hint of how btc can be very profitable especially in the long run. it would've been best if we've started btc early on but better to start now than never
If I am not wrong I saw the price of bitcoin crossing $2900 few days back on preev and that was too high price to invest money in it but comparatively the current price is low and a good time to invest in bitcoins as it surely has an potential to cross $3000 in next few months so even if buy now then we can make good profits in short period of time and if you believe in holding bitcoin for a long term then any price and any time is a good time to invest money in it.
to me i think although when the price of bitcoin was trading above 2900 USD in preev. i think it was also a good time to invest. and now the price is trading near to 2000 USD so it is the best time to invest money right now and do not wast the time and opportunity, because in future we are not expecting any future decrease in the price of bitcoin.