DASH has technically no full block "halving" but rather a block reward decreasing by 7.14% every ~383 days.
This year around 2020/04/27 15:25 is the estimated reduction date/time ( 55 days, 6 hours, 24 minutes ).
More detailed info: https://stats.masternode.me/network-report/319079
I don't know how much of a boost Dash and ZEC are going to get as a result of this decision from Binance. It is one of the largest exchanges out there and we can expect a lot of impact. But both these coins have performed rather poorly for the last 1-2 years. And this has happened despite them showing a lot of promise during 2017, when the bull run was ongoing.