Apple has detailed its upcoming operating system pretty thoroughly but has yet to announce when, exactly, users will be able to try it out.

But, according to a report from 9 to 5 Mac, Apple has asked some of its retail employees to prepare for overnight work on the 24th — leading to speculation that the new operating system will be available July 25. According to the report, the overnights will consist of a few employees putting the system’s master image on every Mac in store.

Then again, the blog hedged, it could be just a run-of-the-mill overnight. The launch shouldn’t have much to do with Apple’s retail stores, anyway, since Mountain Lion will be distributed via download from the Mac App Store. The system will cost just $19.99 to upgrade and is finished and already out in its final Golden Master form to developers.

CNET added some historical context to lend credence to the rumor, pointing out that Apple released Lion the day after its earning report. With Apple set to share its latest earnings on the 24th, a 25th release date would set a nice pattern.

Mountain Lion furthers the design and functional ties between Apple’s mobile iOS system and its Mac system.

The new system will have — among other features — voice dictation, iCloud Documents, a new notification center for the Mac, will replace iChat with iMessages, and will add the Game Center to the Mac to sync gameplay across devices.

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