Real-time clocks: Does anybody really know what time it is?
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A practical critique of real-time clock (RTC) chips from an embedded systems perspective. Most RTC chips store time as calendar structures (year/month/day/hour/minute/second) rather than as a Unix epoch offset, forcing engineers to write complex conversion code for interval arithmetic. The post explains the tradeoffs between structured and offset time encodings, details the challenges of atomically reading multi-field RTC registers without race conditions ('The Dance'), discusses subsecond resolution limitations, and covers UTC vs. local time pitfalls including DST and leap seconds. The author's wishlist for an ideal RTC chip includes: epoch-offset encoding, a 15-bit subseconds field, an explicit snapshot/capture register, and offset-encoded alarms.
