Today's reminder is the second such notice sent out to developers ahead of Apple's planned migration to a comprehensive 64-bit App Store. The company first announced 64-bit requirements for iOS 8 in October.
In a similar note posted last month, Apple made a distinction between new titles and app updates, saying 64-bit support would be required only for first-time submissions. Along with 64-bit code, newly submitted apps also need to be built using Apple's iOS 8 software development kit.
Developers looking to update existing apps have until June 1, 2015, to build in the same 64-bit and iOS 8 SDK support.
When the iPhone 5s debuted in 2013 carrying the A7 SoC, Apple became the first company to deliver 64-bit processing capabilities in a mainstream mobile device, a feature widely dismissed as unnecessary by the industry at large. After a brief period of denial, and a glib statement from Qualcomm, chipmakers modified their mobile hardware roadmaps to adjust to Apple's aggressive rollout.
According to some accounts, the A7 "set off panic" for chipmakers, partially fueled by pressure from OEMs reluctant to fall behind the innovation curve. For example, Apple's smartphone and tablet arch rival Samsung quickly pledged 64-bit support in future devices shortly after Apple's A7 announcement.
The latest iOS 8 SDK is available through Apple's Developer Portal as part of the recently updated Xcode 6.1.1.