I am in 1099-B section in Turbo tax Deluxe. My form 1099-B has various in box 1c for Date Sold and Turbo tax will not accept it.

you were supplied an incorrect 1099-B. Is this for cryptocurrency ?

So, if it is long term gains, just put 12/31/2018. That will not change your filing at all.

If it short term, you will need to put a date less than one year from when you purchased.