Actually there is no exact month or date as long as the coin is cheap then its time to fill your bags especially now its time to invest.
When we looked at the crypto in the 2017, the most crypto price goes up in price in the BER months, the price go really high and investors really earn huge amount of money, and if we will compare it, maybe this BER months of 2018 will be the most good time to invest, just my thoughts.