In plain English
FAR 52.214-15, Period for Acceptance of Bids, is a solicitation provision prescribed at FAR 14.201-6(i), most recently dated Apr 1984. The complete official text is reproduced below, verbatim, from GSA's published FAR source files.
Its text contains no sentence requiring insertion into subcontracts; see the flowdown section below for what that does and does not mean.
Does it flow down to subcontracts?
No flowdown mandate found in the clause text
This is a solicitation provision — it applies to offerors when submitting an offer, not to contract performance, so subcontract flowdown is generally not the operative question for it.
Where it's prescribed
As prescribed in 14.201-6(i), insert the following provision:
Prescribing reference: FAR 14.201-6(i).
The official text, verbatim
As prescribed in 14.201-6(i), insert the following provision:
Period for Acceptance of Bids (Apr 1984)
In compliance with the solicitation, the bidder agrees, if this bid is accepted within ______ calendar days (60 calendar days unless a different period is inserted by the bidder) from the date specified in the solicitation for receipt of bids, to furnish any or all items upon which prices are bid at the price set opposite each item, delivered at the designated point(s), within the time specified in the Schedule.
(End of provision)