Time Throughout the Ages
summary
A concise history links sundials, water clocks and Huygens’ 1656 pendulum to quartz watches (Warren Morrison, 1928) and the atomic definition of the second: 9,192,631,770 periods of the caesium‑133 transition, plus leap seconds and GPS satellites for distribution. Practical rules: use naive vs aware dates correctly, prefer timezone libraries over manual offsets, use UTC for instant math but local calendars for billing, and watch edge cases like Samoa 2011 shift and a pro‑rata refund example that returns $26.79 for Feb 15 cancellation.
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