I know the new reboot has been cancelled of Double Dare. I heard though they have 4 Halloween episodes and 4 Christmas episodes has anyone heard when they will air? Thank you

They'll air them as expected, I guess.
http://nickalive.blogspot.com/2019/08/nickelodeon-cancels-double-dare-revival.html

The Halloween episodes are airing on the week of October 21st all at 7PM.

If the ratings are good. Why are they ending it?

https://twitter.com/realmarcsummers/status/1167863904371822592

here's tweet from Marc Summer that was announced cancellation last month.

"Double Dare on tv has been cancelled! Eight more shows will air in Oct and Dec but then it disappears. So this becomes my FAREWELL TOUR. Last time I will ever perform this show. Go to http://www.doubledarelivetour.com and book some seats. After Dec 22 I’m done!"

Last year Jun 2018 Double Dare reboot premiered before Brian Robbins was in charge. And new season premiered last March.

nick will air the Final 4 Double Dare episodes,Holiday Edition
Friday’s at 9pm.

Episode 1 November 29, Friday 2019 9pm.

Episode 2 December 6, Friday 2019 9pm.

Episode 3 December 13, Friday 2019 9pm.

Episode 4 December 20, Friday 2019 9pm. (Final Episode)

wow.. i never knew why they air on a Fridays at 9PM slot instead of doing daily weekdays like Mon-Thurs slot.. oh well. i hope Nick airs those promo soon.