Per the IRS Instructions for Form 8949, page 5:
Stock acquired on various dates. If you sold a block of stock (or similar property) that you acquired through several different purchases, you may report the sale on one row and enter "VARIOUS" in column (b). However, you still must report the short-term gain or (loss) on the sale on Part I and the long-term gain or (loss) on Part II.
TaxAct® supports "Various" as the date acquired on Form 1099-B. Enter "Various" for the date acquired, then enter the cost basis, date sold, sales proceeds, and select either short-term or long-term.
To enter Form 1099-B for your capital gain or loss transactions in the program: