On your marks, get set, save $100 on a 16GB iPhone 5s if you buy one from RadioShack, starting today.
The deal gets a mite sweeter if you have an iPhone 4S, in which case RadioShack will hand you an iPhone 5s for nada, crediting you $100 toward the existing $100 deal, which of course equals nothing. Well, the sort of nothing that involves a two-year contract, anyway, since both the $100 standalone and $0 for trade-in deals are limited to contract-arians AT&T, Verizon and Sprint.
As noted, the promotion starts today, April 18, and runs until take-your-best-guess. MacRumors quotes a supposed Radio Shack source as saying "the promotion does not currently have an end date."