Hakone free pass for use two days later

If I buy the hakone free pass (2 days) at shinjuku station, but use it 2 days later, is the hakone free pass still valid?

Probably possible at the ticket counter. But why? You can easily buy it on the day of travel.

You can buy a post-dated pass at the ticket counter.
Reason can be simple, especially if you want to book Romance Car and concerned about getting seats.

Good point.

Slightly related and maybe of interest to the OP:

The pass is now also available as an e-ticket:
https://www.odakyu.jp/english/passes/digital_tickets/

And Romance Car reservations can be made online:
https://www.odakyu.jp/english/romancecar/e_romancecar/use/

@Uji - just as an example, back in April I needed to book 19 seats for a popular time on the Romance Car. Given those seats do sell-out (I've been caught before), I did the passes and bookings a month ahead