iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Apple Announces August 28th Availability of Snow Leopard
"Snow Leopard builds on our most successful operating system ever and we're happy to get it to users earlier than expected," said Bertrand Serlet, Apple's senior vice president of Software Engineering. "For just $29, Leopard users get a smooth upgrade to the world's most advanced operating system and the only system with built in Exchange support."
Snow Leopard is available as an upgrade for users of Mac OS 10.5 Leopard for $29 as a single user license and $49 as a family pack. For users of Mac OS 10.4 Tiger and earlier, the Mac Box Set includes Mac OS X Snow Leopard, iLife '09 and iWork '09 for $169 as a single user license and a family pack for $229. (prices in USD)